wanna go fast!

ok so i have a straight 6 (some say its a 200 others say its a 250) i gotta get the numbers off the block and find out for sure...anyways i have a weber 32/30 carb on it and 3.50gears but it will only go about 40 or 50mph max...what do you guys think it is...someone was telling me that because my van is 3 on the tree the rearend might be for an automatic and thats making the gears steeper than 3.50s and thats why its maxing out...but it doesnt seem like the gears are winding out its just the motor isn't making anymore power...sorry for the long story but i thought i would ask you boys since you guys know your shit

You ARE pushing something with the aerodynamics or a vending machine (LOL) thru the air.
If you don't have a steep rear gear which would limit top speed, I'd also say it's the motor running out of steam.
Find out what it is, and check it's condition.

I have a 200 with 3.50 gears. I've had 70 out of it, but i prefer driving at 60.
Sounds like you have engine issues. Could you rig up a tachometer to see what revs you are maxing out at.

thanks everyone for the suggestions and info..i'm gonna mess with it again tomorrow and see what i find out..

Going fast on LA freeways is always fun....for me stopping fast in a 45 year old van is another story!! I avoid them if I can and when I have to I keep plenty of distance between me and the person in front of me....working on the Donivan master cylinder upgrade very soon!!

Gearing is all about horsepower, and it sounds for sure like you are NOT getting the r's out of your engine. Gearing in this case shouldn't have anything to do with anything.
You first say positively that you have 3:50's in it, and then later you make the point about automatic gearing or stick gearing. There is really no such thing as either. If you run out of pulling power in third at 50 you would have to have like 2:75's or 2:50's in there!!! A strong 200 or 250 with 3:50's should be a little sleeper and pull out of the hole real quick, those are a real good set of all around numbers.
Regardless!!!! IF your engine was pulling all the way out, it would go faster than 50, with a 250 and 3:50's~~~~ I would expect to blow off some other cars easily at a red light, and still buzz along a 75 easily??? With 3:00's and the torque of the 250 you may start to loose the pulling power at the top of a long steep grade, and then have to dump it into 2nd,, but, the effect would be the same, you should then pull the r's up in 2nd until you blew it up.
Something in your tune, or set up isn't letting the motor pull to its potential,, timing, dwell and fine points about your Weber perhaps??

The 250 engine has a higher deck height in order to get the longer stroke in the block, and the block is wider also at the base. The only mounting for a 250 in ours that I have seen on the 170 cross, used the Maverick motor mounts, as the 200 mount needs cutting, re bending, and tack welding back together in order to use them. ,
I would Jack the rear axle up in the air, just to confirm what gearing you really have?? What rear end do you have???? is the gearing tag still on the dif??? Put it in neutral, mark the pinion and the case and turn a wheel and count how many times the pinion turns compared to one full turn of the wheel, that will tell you what gearing you have. Example,, 4:00's would mean the pinion would turn 4 times to one time of the wheel. The CORRECT way to figure gearing is by the OD of the final drive tire, in this case it would be close enough with out using that formula.
Use a Dwell to check your points, its impossible to do correctly with a feeler gauge, it won't take into account worn bushings and or cam lobes in the Dizzy, a Dwell gives you and EXACT number to use,, no guess work?? and wasting time. Then we can get into the Dizzy, initial advance/ full advance at what??? etc... then get into the Weber???????????
Old Skool