RB20,SR20,V8 swap kits for fc3 or mount kits
 

where can they be found?

V-8 kits can be found at Granny's Speed Shop or Hinson Supercars.

Grannys also has mounts kits for nissan vg30 V6 engines, chevy 4.3 V6 and ford 2.3 I4. I don't know of any off the shelf kits for RB20 or SR20, I think those would have to be custom. Might want to check out the other engine conversion section under rotary performance.