I got a 72 Luxury lemans/custom with 7h1 heads, 625 road demon, and edel. Performer. I want more power, but want to stay with pump gas(93). Should i get the heads machined or do head swa. Dont want aluminum heads, want to keep iron. If swapping heads would be better which heads should i look for? Was lookin at 400 6X small chamber? Would 6x be the answer? Can anyone help me out. I do know the car had 160hp before the 2 to 4 barrel and the heads are 2-barrel.