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Do you mean a 300zx? How deep are your pockets? A turbo conversion and remap will get you close but not necessarily reliable, I'd suggest fitting stronger rods/pistons to be safe, engine compression will need to be lowered and uprated fuelling.
Why not drop in the twin turbo engine and you'll be virtually there with a reliable solid 300+ BHP. A breakers yard will probably turn up a good donor unit for you.