Simply, the Z32 can't fit HUGE turbos on it without hacking it to bits. But with HUGE turbos comes alot of lag. Personally, if I DID have a supra and was doing a build up I would try to make it as fast and quick as possible without compromising spool up / LAG. Which might put in in the 600-700 hp range. Exactly what you can do (and I AM doing) with the Z32. The biggest difference is if you want a car with ungodly power and ungodly lag you have to use a supra because the Z32 won't support such large turbo(s). When I use the term street car, I take it to mean a car that does everything well including response. Once you make a 3.0L engine make that kind of power, it will no longer be fun to drive on the street (way too much LAG). So it is no longer a good street car. With either the Z32 or the Supra you could make a 10 second 1/4 mile car that you could also take to the road course, and for that application (all purpose no compromise -read: extra lag-) I personally prefer the Z32.
To each their own.
m a g l i t o parts are FINALLY here - engine is going back together NOW sig photo by me effects by ZXRider(SoCal)