anything in excess of 300++whp is risking it quite badly. although there are some people who had done this before, more attention should be made in maintainance & while driving it (i.e. always check AFRs, fuel press, maybe oil press etc.).
with race gas and a good tune you could probably make 500whp, how long will it last? who knows... anybody shooting for 350whp reliably should install forged pistons and head studs and minimum.
Ive got arp head & main studs already so i'll be ok there then. Ime looking in to pistons at the moment, ime probably going to get a set of weisco's. Ime also going to be running the car on 99ron fuel.