too mild camshaft
currently dynamic compression is down to 7.75/1
maybe get a cam that closes the intake sooner...the power is already down with that static comp to start with, though comp says that 10-1 is fine...I don't know what they base that on.
63 dartman, 600 hp is no prob for the block, I believe the limit at this level is more related to rpm than the actual number of horses. the higher you spin the crank, the harder it is to keep in one spot