That would be an interesting project!
For the engine, maybe a Northstar?
https://en.wikipedia.org/wiki/Northstar_engine_series
I think some guys have put them in Fieros with the manual transaxle too.
For the body, you could try Humster, they will sell you a 3D model and will send you a file with slices to build a buck.
https://hum3d.com/3d-models/lamborgh...a-p400sv-1971/