whats the dif? 350 crate engine years

I have a 92 caprice w/tbi. I found a used crate engine I may buy BUT I dont understand what the years are for... like jegs base says pre-76 then another 85 earlier or 85-92 is there real dif ? or mounting and acc. relocation? How can you tell what will work? thanks for any input.
flip

ASk these guys, they they can set you up with the exact motor for your ride

http://www.crateenginedepot.com/store/Which-Engine-is-Correct-For-My-Vehicle-P769C3.aspx