there are several changes throughout the years but they will all bolt up and work just the same. the newer ones have the return oil line moved back a few inches above a bearing i think to help lube it. but i think thats the only real external difference your going to see afaik... i just threw a 95 80e out of a 1 ton van in my truck. needed a full rebuild but it works great.

and yes any 3/4 ton+ truck/van will have it. i think some 1500's may have but im not sure. to be safe just look for at leas a 3/4.

you can verify by crawling under and counting pan bolts. 60e's have 16 and 80e's have 17. if you dont want to get dirty and know for sure its the original trans then look in the glove box for the RPO codes either MT1 or MN8. those are for the 80e's

hope that helps your search.