Can't be done. The set-up is different since it is a rear wheel drive car.
Err! Correction. I should have said, "It could be done. Anything can be done for the right price."
You need to go with a GTi-R or BlueBird DET engine. Both of those are front wheel drive compatible. From what I have read, the BB DET is the easiest swap to do and it bolts right up to the manual gear box.
Geo, a fellow forum member and staffer of the G20.net did such a swap in his G' and it was featured in a recent issue of Sport Compact Car.
Thanks, I saw a heavily modified 400+ HP silvia in Sport Compact Car one time... I knew it would be mighty expensive because of the rear wheel drive conversion...but that kind of power would be nice huh! If only I had the money....