250 rebuild or long block?

I've been looking and asking around about someone locally who would or could rebuild my 250. Unfortunately all I'm finding are guys that want to put a Jasper engine in.
When I started tinkering on this van I thought getting the motor rebuilt would be no problem. It seems hard to find any shops that will deal with it at all. I did have one guy hold it for 3 weeks and then said $5000 for a jasper.
For as many of these 250s that were made it would seem like there would be some rebuilt long blocks available?
Mine runs good starts right up but smokes like crazy. pretty sure its oil, don't smell the anti freeze/steam. but it smokes at idle and looks like a contrail going down the road. lots of oil build up in the tailpipe too.
Don't really want to do the v8 just trying to put the van on the road in original configuration.

if you got an automatic, the vacuum modulator could be leaking causing the smoke,,,,,,

Thanks Donivan, it's a 3 on the tree. It sat for 12 years. It's the original motor based on the engine vin code so I'd like to keep it if possible.

if the rings froze up, maybe run some Marvel Mystery oil in it and see if it helps,,,,you can change the valve stem oil seals without removing the head if you got the right equipment,,,,,,or have the head rebuilt,,,,,,you got options,,,,,,,,,have you run a compression or cylinder leakdown test to see if you find any problems,,,,,,,,do you feel a lot of blowby out of the oil filler cap when the engine is warmed up?

S and J in Spokane sells 250 long blocks for $1227 + 250 core fee + 195 shipping. 7 year/100,000 mile warranty. My old employer uses S and J for Mercruiser engine swaps. Only time we had a problem was when the boss put an oil pan on one with a near rust hole in it, it opened up at some point and the guy ran it out of oil and it seized. DOH! He was always trying to save a buck, even when it made no sense. "we don't have time to do it right but we've got time to do it again" type thing....

https://www.sandjengines.com/rebuilt-auto-truck-engines/search?&year=1969&make=CHEVROLET&model=G10_VAN

Thanksy guys.
I don't see any blow by while running. I changed the oil and put a quart of marvels in then. Haven't noticed any improvement but I've only put 10 miles since then.
Just got it back from my last try with mechanic shop. I thought the guy was going to do the compression and or leak down tests to determine if it was the head or rings. after 3 weeks his secretary called and said $5000. so I went and got it. $200 bucks for his time. no findings no tests just "you need a new motor" geeez
so I've had 3 bad experiences. can't rebuild it myself but I could probably manage a motor swap.
I could do a compression test myself but I think it's gonna take a leakdown test to tell much.
or just pull the head and get that done and if it still smokes get the low end done.
Those long block prices sound reasonable Seth.
The motor looks to me like it's never been out so it's not beyond the stretch of imagination that it could be flat worn out.
I just figured it wouldn't be this difficult to find a mechanic that could work on one of these old 6 cylinders. I guess I' could try a place like firestone for the leak down test. I'v been trying independent guys.

,,,if,,,,,,it smokes white,,,,,,,and you dont feel pressure coming out of the oil cap hole in the valve cover, then I would think the rings are still good,,,,,,,,,most likely cause then would be valve stem seals,,,,,,we fill the cylinder with air to keep the valves from falling down onto the piston as we take the valve cover, rocker arm and valve keepers off to replace the seal,,,,,,,I surely dont like having to re adjust the valves,,,,,,,so thats one option for you,,,,,,,

Is there a fitting to put air into the cylinder? Through the plug hole I'm guessing?
If I were able to pull this off, not sure I have the skills/ talent, valve adjustment would be necessary after reinstalling the rocker arm? Just wasn't sure about your comment about not wanting to adjust the valves. Thanks for your input Donavan

run a compression test, record all numbers, then spray liberal amounts
of wd40 into each plug hole and run compression test again, any cyls that
increase have ring issues.
when I say liberal amounts I'm talking about a good 5 second blast into each
cyl. oil will help seal rings to the cyl walls, it will not help seal a burnt valve

Ok, thanks y'all. I'll give it a shot.

we can get you through any hard spots you might run into,,,,,,,I guess peoples have stuffed rope into each spark plug hole to prevent the valve from falling down after you remove the keepers and spring,,,,,you will need a valve spring compressor,,,,,,,when you take off the valve cover and start the engine, the lifters squirt oil 6 feet  out of the engine,,,,,,I have a spare valve cover with holes to adjust each lifter with plugs in it,,,,you can count the turns on each rocker and put it back the same,,,if,,,,,,,the valves were adjusted correctly to begin with,,,,,,,

Most parts stores will loan you a compression tester.

Which seals to buy? Are intake and exhaust the same seals? Do you still use the o ring if you are using umbrella type or is umbrella in place of o ring?
Thanks

Just swap it out for a good running used 250.  Most people throw these engines away, or close to it, still when the do a v8 swap. I would not spend much $$ on rebuilding an inline six.  

Here's one that runs good for $100

https://bham.craigslist.org/pts/5724612069.html

Thanks for the pics Donivan.
So, I got a compression tester. looked pretty good for a while. first 1-3 ranged from 120 - 150 pulled number 4 plug was bent closed probably not firing but still in the range above, same with 5. got to six and 5 lbs. amazing how well this motor ran on 4 cylinders. so no comp. in 6. I thought maybe stuck valve? pulled the valve cover and the rocker arm is off of the push rod. feels like the valve is moving some. push rod seemed stuck on the high side so rotated to closed valves and gave a little tap with a piece of wood and it dropped in a bit. not sure of the cause but the stud appears to have pulled up in the head. the nut is at least as far down the threads as the other rockers but the stud sits higher and I can get get my finger between the rocker and the top of the spring. Can the stud be replaced in the head. I'm guessing this could have been cause by some other interruption at the valve or lifter?

I'm not sure which valve is which but it is rocker 11

after manually compressing the valve spring a bit, the compression is now 150 in #6.
push rod is moving correctly.
The van sat for 12 years at least. that was the last tag registration.
could a stuck valve have caused the the stud to pull? but the valve would have been stuck open to have no comp?
I'm thinking if I can get the stud back down the it might work? interestingly, the plugs were relatively new and all looked good except #6 which was still shiny new. don't know if it was sparking at all yet but might just not have been combusting do to no compression...?

Replace the stock press-in rocker stud with a screw-in stud.

This involves cutting new threads, so there are metal shavings produced. For this reason, it might be a good idea to remove the head from the engine, but maybe if you use a shop-vac while cutting the threads, you can be clean enough to do it with the head still installed and not get any debris into your engine.

Here's a good youtube how-to vid.

https://www.youtube.com/watch?v=ITah_y8MXgM

I carefully tapped the stud back in and reassembled everything. Runs sweet and 90% less smoke! I still need to do the valve stem seals but at least I can test drive without looking like its on fire.

it aint going to stay,,,,,,,you might drill a hole through the side and put a roll pin in it to keep the stud from sliding back up.........

Yea, that's what I figured. I've read about that and the tap and screw studs. At least it gives me a better idea how it should run. Been out driving for most of the morning. Runs good for the moment.
A little noisy in front maybe water pump or timing gear?

when the engine is cold, take the fan belt off and run the engine,,,,,,this will stop the water pump and alternator from turning,,,,see if they were causing the noise,,,,,,,

These engines are noisy, probably lifter chatter, after you do the head work and guide seals, pull the side covers and check that lifters aren't stuck or collapsed, they are inexpensive, available and replaceable from the side, just had mine done, still a little chatter, a bottle of STP and running 20-50 oil stopped almost all noise.  This might involve re-adjusting the valves, but if you get it close, a local shop shouldn't charge that much to do a final adjustment for you if you are unsure..a set of feeler gauges are cheap but nothing beats experience....Doni will atest, isn't the timing gear fiber and usually not a source of ticking?

Thanks for the help and helpful tips & tricks folks. I finally feel like I'm making headway, and getting to cruise this thing a bit. Picked up a fridge, delivered it to my sign shop, took the girlfriend out to lunch and landed safely at home. Had one near miss with a city bus because my brake pedal was loose and I learned it won't depress when rotated to far. Got that settled immediately upon our return.