Not much mod required my 6yo daughter can do it. I put a 90 set in my 80 with out issues. The front end to swap to the 87 style isnt hard either. You might have to buy a new set of fenders to match the front end though as my stock 80 fenders don't line up right(cheap on ebay or online somewhere if ya take your time to look)
I turned my 80 into a 87-93 style frontend rearend quarter windows you name it but the dash is a 87-93 style.