need some help here, i bought an 87 rx7 that a guy had started swapping a 91 turbo motor into. i bought it from him and now im trying to get it going but i have been reading and from what i can understand you can pretty much only use the block, and i was wondering if there was any way i can get it to run, i will swap in another motor if i have too but i really dont want to

 

Here are two links that may help.

Rotary Resurrection: Differences between 86-88 (S4) engines and 89-91 (S5) engines

Rotary Resurrection: Swapping an 89-91 (S5) engine into an 86-88 (S4) car