What to look for when buying a transmission...

I'm in the market for a 727 for my big block 66 Fury. I don't have the kind of money to buy an ATI or a Cope trans. So if I'm looking at a transmission that he seller claims has been rebuilt, what should I look for? Should I pull the pan? What questions should I ask the seller?
Thanks

If it was me, I'd stay away from privately owned rebuilt but-never-run transmissions unless you know the rebuilder. It's one of those things that if there is a mistake, you dont find out until a lot of time and some money is invested. You should see receipts, and I'd want to pull the pan to look at it. Preferably, find a local shop that can do it witha warranty. Then you save shipping and get a warranty. Just make sure you don't have it don so early that the warranty is up before the car is able to run/drive and make sure it's good.

Thats excellent advice.I just had my tranny rebuilt by a local shade tree guy who was recommended.My trans is still not right and now I may have to pull it again.Get it done by a reputable shop with a warranty.