Well... I'll be the first to say that I'm stumped fellahs. Those pistons in the pic above look ALLOT like what I remember from the 85 and I cannot recall specifically what the 89 had in it (wasn't paying that much attention). Rick91GT may be able to help out a bit more with what's what. If it were me and I ever planned on forced induction, I'd go ahead with the 85 pistons you've got (regardless of what they look like) and maybe shave the heads to get your final compression ratio to where you want it to be. With the 85 pistons you have.... Are they shorter than the 87+ slugs you have lying around?