You are better off lowering the compression down to around 7.5:1. The CVH is 8.3: as standard. Lowering the compression will alow you to run a higher dynamic compression ratio while reducing the risk of detonation and reduced heat as you can run more ignition advance. You will lose a little off boost torque by lowering the compression but I beleive it is better to reduce it rather than raise it.

300bhp from the CVH is certainly possible but you will need steel H section con rods.