i agree with everyone here, vortecs or i prefer aftermarket vortec style heads, especially the RHS 170 pro torkers, they out perform the origianal vortecs and are not prone to cracking like the original vortecs. the intake would have to be vortec compatable, they are close to the same price as regular style intakes. however i wouldn't go with flat top pistons as with a 64-65cc combustion chamber would give you a low to mid 10:1 CR i would likely try to stay closer to 9.5:1 for a only street vehicle.
making 325-350hp out of a 327 will be easy due to the fact that 327's like RPM's 350tq is still very possible.
as far as head flow i would look for a head that flows 240+@ .500" lift and has a good consistante increase from .300" lift up, stock vortecs will fall slightly short of this but not by much, but the RHS 170 heads will be right on the money