I just did a 408 with an eagle balanced steel crank-hbeam-mahle piston kit and the pistons ended up between .003 and .005 in the hole... block was that straight. With the eddy 58cc ( measured) heads, and a .036 cometic gasket it has 9.84 compression. The pistons and head cc are the big difference between la and magnum, make sure you get what compression you want, the blocks are shorter so an la non dished piston and magnum head could get you 12.00 compression.