Change the cylinder head to the hemi head. You might have to get the hemi pushrods as well. They could be different in length. If you are looking for more horsepower, the non hemi is a.better starting point. Valve to piston interference
is very common with higher lift cams, and or raising compression ratios by milling the head, or installing a longer connecting rod. This is caused by the canted angle of the valves in the hemi.
