Depending on how big of cam you go with, you might need to fly cut the pistons. You building the engine yourself? I would check the valve to piston clearace, you need about 80-100 thou of clearance.

If you shave some material off the deck (straighten the deck out), helps with increasing compression. Building these old mopars aren't cheap. I would forget the tune and go with a carb, just easier/cheaper.

 

I am building it myself and have in the list to check the valve to piston clearance. I built motor before just never a Magnum. Carb isn't even a thought because I hate them. I like fuel injected.

 

If you are getting new pistons that won't be an issue. You can get them with valve cut outs. If you go with Keith Black pistons be sure you install the rings to the manufactures specs. I have seen them break off the top section of the piston above the ring if done incorrectly.

 

Reusing factory pistons