Buying a used 700r4 question

[LSUMurse]

I am looking to eventually buy a used 700r4 and stick it in my '68.

My question is:

If I purchase a 700r4 that came out of a truck, from 87-92, do I need to do all the upgrades that are typically necessary to put them into our trucks? It seems that if they were in a truck already, it should be able to handle my truck. Obviously, I'd get it rebuilt for piece of mind, but rebuilding it to stock should be a little cheaper, I would think. I am not planning on rodding this thing out. I may tow a small camping trailer, but nothing over 16'.