Ken - My brother's R33 made 466rwhp on 20psi with an externally gated GT35R.
Basically he had bolt on mods - hks cams, hks exhaust mani, greddy copy intake plenum, xf falcon throttle body, external gate, custom exhaust system, standard pistons, rods, rings, crank etc, standard rb25 gearbox and standard rb25 diff.
That motor is still going today, 5years after it was built and it has never had one single problem.
RB25's are good for 500rwhp on stock internals, trust me.