What do i look for in a junkyard tranny?

[JORGIE95961]

Transmission that is!! lol? no ok... Seriously though.. im gonna set out to find a junkyard th350.. now I know some of you will say.. there at a junkyard they are junk.. but ive scored trannys before out of yard that have lasted for th elife of my cars.. The big questions is. what di I look for ? Is there anything about a tranny that can tell me its shot?.. id like to have at least an %80 chjance of it working versus the old 50/50...