915 heads vs 302 heads

Well those heads aren't cheap

But don't they come closed chamber and around 62cc's, you could mill them .030--.040 and find a .030 thick head gasket. The larger ports should be good for a few hundred more rpm with the same cam. A large port single plane intake might help also, the victor is super-don't be afraid of losing power down low, not with those gears

http://www.ebay.com/itm/Edelbrock-V...Parts_Accessories&vxp=mtr&hash=item35bb56cb35

Even if those heads can be milled more then .040 not sure I would. It kill the re sale value and if you ever change the pistons you might regret it then