Help with sb combo

I think, before you spend too much on anything, you need to find out what you have there. 7.40s is no real slouch and if the heads can move some air you might as well take advantage of it. Same deal with the pistons - If you can calculate the compression based on actual chamber measurements, and actual piston/bore measurement (1" down method) then you know what you have, and we can help a little more. So I'd have the heads really checked out - see what they have for flow, spring capabilities, and chamber size. While a head's off being tested measure the volume of the piston/bore combo, then go from there.