To my knowledge Chev never put the Super T-10 in a vette. They made their own transmissions (M-20 -->M-22). So I doubt the owner knows just what it has. If it should have a Borg-Warner in it then it is either a very old non super, trany or a transplanted aftermarket Super T-10. but it didnot come from the corvette factory with it. sounds like a car that you should have a very experienced vette person give the car a good going over before you buy it. Mind you most of these guys selling something out there don't have a clue what it really is. I am sure that someone on this forum must live near there and you might get them to go look at it with you. Most of us on here do like to go look at strange cars just to see what is out there. You just never know when you will find a diamond in the rough or a Yenko in a barn.
Either way good luck and be sure what it is before you plunk down your hard earned money.