To Rebuild or Not to Rebuild...

So I have a 240 in my e-van, and it leaks oil a bit. starts up alright, but I just want it to be as good as it can be, ya know? So should I have it rebuilt? The old owner said the owner before him had it rebuilt, but who knows how long ago that was? Anyway, just want this van's engine to be as trustworthy as possible! PS: I live in Los Angles if anyone knows a good rebuild shop.

Have a compression test done. If there is a problem with cylinder pressure shown in the comp test, have a leak down test done. That will tell you if the problem is in the head or the rings. Does it burn oil or smoke out the tailpipe?

Being told an engine was rebuilt could mean anything from rebuilt completely to a back yard valve job and quick cylinder hone and rings "freshening up", or nothing at all aka rattle can paint i.e. "Tijuana Tune Up"

no burning oil or anything like that. It overheated the other day, so I think something failed in my cooling - radiator, pump, thermo maybe? I will be putting in a taurus with a larger alternator for sure. But I did drive for like 1/2 a mile after overheating trying to get home (I know now that was a BAD and STUPID thing to do). It ended up dying at a red light. So now my concern is a head gasket. IF that is the case, and they have to pull the engine to fix that, I was thinking I might as well have more work done so all I'm paying for is labor at that point.

What about going with the more modern 300....I hear that it's a bolt in replacement, or very little work at best to put in. Probably cheaper to rebuild down the road as well. And also gives a little more torque as well.

That's a good point, if it does need rebuilt it's the perfect time to go to a 300. I'm not sure of the intricacies of the swap, I think any 70's 300 will swap, most 80's, not EFI, they changed some things on the block. But, if it aint broke.... Let us know what your compression test comes up with. You can probably do a free compression tester rental at autozone, oreillys etc. It's easy to do, helps to have 2 ppl tho. Run the engine to normal temps. Remove all the spark plugs open the throttle wide and crank with the tester on each cylinder and record the data. It's best to unhook/plug the fuel line. And definitely pull the coil wire.

ended up being a head gasket. mechanic said a full rebuild not necessary so just doing a valve job. But throwing in a new radiator, Taurus fan, too. thanks for the help buys. If / when the engine does finally give up, I will for sure go 300

Leaking is common with any 50 year vehicle, have the pan dropped too, check the oil pump. new gaskets and main seal may be all you need.  As for cooling, have the radiator checked for flow at a shop.  Mild cases can be boiled out, severe, get it re-cored or get a new one, then the stock fan should be fine.  Adding an electric fan to an old clogged radiator won't do a thing, it will still run hot. I'd go in steps, see how hot it runs with the new radiator first, only try a fan if you need it.