What Engine to go with

A real VS29L4 should not be cut-on , imo . Not many made , not many left .
best answer. if it's the OEM motor. set it aside. build something else and drop it in. save any parts you remove and try not to cut up the car too much. in ten years you or someone else will be very happy you did it this way.
... take it from someone who's killed a lot of original cars and wishes he had it all (well, ok some of it :) ) to do over again

chuck