scott, stage 3 ported heads are the max i would do, that still maybe more than your stock cubes can pull through though. for your set up though i think the stage 2 IPS heads would fit the bill nicely. match that up with a LS6 intake if you can (or port your LS1) and you should have a decent flowing setup and good port velocity to get the max air into the cylinders and make good power across the board. mine are stage 2, i think i still have the flow chart for them if you want to see it.