Well, something doesnt make sense...I dont think your block can be decked .060, when the 'average stock' deck hgt is something like .025 or .030...at .060, your pistons would be out of the block by .030 at least. And .060 off the heads would leave the intake valve edges below the deck surface of the head. I had a set of 781's milled about .038, and the intakes were just at surface level. Is it possible you messed up your numbers? And as far as the heads being too big, No...not a problem. The intake runner size is what determines your air velocity. For a smaller cube big block like yours, you dont need much runner size. Those 305cc AFR's for example, are pretty big. The 781's should be about 256cc. That's all you need. The original heads (closed chamber Im sure) that came on your engine were about the same runner size, so that's where you want to stay. Dont go too big, or you will start to lose you low end torque. I dont know too much about the % of intake to exhaust flow, but for what you're doing, dont get too hung up on it. They will be fine whether you go with the bigger valves, or stay stock. What KB pistons do you have?? That will help to figure your c/r with different heads.