Their calculator is pretty good, but you can always send them an email too. I sent a few messages back and forth with a tech at KB to get a better estimate for my 340, since the tops of the pistons (KB243's) were actually over the deck of my 340. Since part of the piston was over the deck, but the valve reliefs weren't entirely, and the shoulder of the piston was pretty much 0 deck, it got a little bit more complicated then the generic info on the piston. But they were very helpful, and I got it figured out. :-D