Will any aftermarket parts, such as springs or body kits from the 1st gen Prelude fit an 86 XT, either with or without simple modifications?

Any of the non-picnic-table-sized rear wings. But that's about it. You'd be better off looking at what people have done to their ER27s and their Imprezas, and adapting those mods to fit your needs.

im pretty sure that the GEN 1 prelude body kits will fit at least in the front if not the whole car.

 

i remember somebody doing this over on the XT6 boards.

 

wagons only, impreza body kits wont work and nobody does anything interesting with ER27s except kevin thomas.