I'm talking front diffs, tranny, transfer case etc.

CHeers guys

 

Maybe not directly, but I don't see why you couldn't find adapter plates for some of it. Not sure what all you're wanting to swap, but I think it's 80-96 that's interchangeable.

 

The front differentials are both Dana 44s, but the diff in a 91 is a removeable third member. The differential in a 79 is part of the axle. I am pretty sure the carrier inside a 91 third member can be put into a 79 differential, but the outside axles are totally different.

The rest of your questions require more details for answers. Which tranny?