OK, I got the heads off and looking at things closer, the phase 2 motor has flat top pistons that are flush with the deck, while the older one has a dished piston that might stick out past the block a couple mm's. Head volume on the phase 2 motor looks to be less than the older one but can't really tell. Now my concern is if I am going to loose a bunch of compression going to the dished piston. any ideas???