I like your optimism, but lets look at the math and see what we come up with.
Supra Mk3 weight 3389lbs (wikipedia weight I am sorry, might not be accurate)
260Z weight 2425lbs (zshop.net.au values)
Supra with 700hp is ticking time bomb.
So 700 x 3389 / 2425 = 978 hp.
So if your aiming for 1000 hp then you might be in the same ball park as the supra guys. But hey, I guess you can always replace the gearbox if that happens.
Oh yeah, get the damn thing on a dyno and stop messing around with a street tune man, don't want all that hard work going down the drain (especially when your playing with big horsepower, boosted air pressure and explosive gases NO)