So i bought a motor that was thought to be good and it needs a rebuild, but i can buy another motor cheaper than a rebuild.

I have found a motor for 200 bucks, its a 5.3 and the guy ran it hot with 150 miles on it. The thermostat stuck and he said it warped a head. Now what do i look for when going to get this motor. I don't need to busted motors and all directions say that this motor's bottom end should be good and i can use the old heads off the other motor. Whats yall's suggestion?

 

For 200, I'd leave it.
If one head is warped, the other may be cracked and warped too. Might also have a warped or cracked block. Depending on how hot it got...the crank might be warped too. (You don't know how hot the babbit of the bearings got, so you might have a foobar'd crank)

There's really no way that I'm aware of to tell if theyre are warped without completey tearing it down and measuring.
Abouot the only thing you can do, is spin the crank around and see if you have any heavy spots (With the plugs removed). If you've got heavy spots, it could mean the rotating assembly is binding - which means, you bought another paper weight.

Thats just my suggestion though.

I found 5.3's in Michigan in good running order for $250-300.
I'd consider yours a "Core" motor, and worth about $100 bucks.

I'd save your money and get a known good running motor. Either from a salvage yard (with a warranty) or one that's still in the vehicle that you can hear run.

Example off of car-part's website: 01 GMC 5.3K, 69K miles $800
There's also one on Craigslist for around $300 and it's a runner.

In short...there are PLENTY of 5.3's out there that havent been cooked. Save your cash and get a known good one.