can i swap
 

all my parts from my 87 to an 88 or 89 maybe even 90?

86-88 = Series 4
89-92 = Series 5

Far from all the parts are interchangeable between series. You also have to consider the trim model (a.k.a turbo, convertible, base, etc.).

Rotaryresurrection.com way be a little more helpful.

i don't see why not. just remain in the same series... s4 w/ s4, s5 w/ s5. some parts are interchangeable but save yourself the time and headaches and find a same series parts car.

anyone know where i can find 88 or 87 rx7 shells..?

What does "all my parts" mean? Some parts will swap cross series, some will not. In general it's a pain to swap an engine or an electrical part cross series, but many of the other parts (trim, body, etc.) will swap.

What are your plans with swapping. Are you talking about engine wise?

Basically, most suspension and drivetrain will swap. Most electronics, fuel injection, etc. will not swap.