The only things that are not interchangeable with yours are some 84 parts (doors/door skins, and anything having to do with wiring) and 88 brake and suspension parts. 87s and 88s also got different headlight motors and wiring, and different gas tanks. The 87-88 four cylinder engines are different enough to not be a direct bolt-in.
Other than that, most everything is fair game. Enjoy.
And welcome to our obsession!
88 Formula IMSA Fastback. 4.9, NVG T550
Praise the Lowered!