10.1 compression with alu heads that will work
stroke to 496
go as big as you can on cam are you running dry or wet tails?
Turn til 5800 may have to use a single plane for the rpm but I think an air gap will work and you will keep good strong low speed trq.
A true 600 is not impossible but 1 to 1 power ratio is very easy and a starting point in what will have to be done. So gaining 100 hrsp will take work.
I did a 496 set up and it made 560 and was reliable as hell only turned it 55 5600 so not too push it too hard.
bigger ci+ comp+rpm= more hp