I believe you can interchange them up to 1987, after that I think you have to change the radiator support. should be bolt in. I just put a 82 front end on my 76 blazer, and I have been playing with a few different year grills and they all seem to fit fine.
you might have to play with your turn signals , depending on which setup you settle on. ( move from under single light to behind grill)
good luck.
hope this helps you out.