560 would be about the theoretical maximum assuming it's designed to last more than a few hundred miles, but @Dammit has talked about wanting a sensible, tractable road engine so I'd say 80lbft a litre is a good target, which would give 500bhp at 9000rpm.
I seriously doubt anyone would build a n/a road car engine to produce max power at 9000rpm so yah, I'd be happy with a reliable and accessible 400hp at 7000 😎
560 would be about the theoretical maximum assuming it's designed to last more than a few hundred miles, but @Dammit has talked about wanting a sensible, tractable road engine so I'd say 80lbft a litre is a good target, which would give 500bhp at 9000rpm.