Heads issue

Hi, I'm presently building a 340 also and your pistons look like flat tops. How did you get 13 to 1 ratio out of them. my pistons are positive decked about .030 over the deck. I have stock X heads. Am I going to have to much compression to run on weekends to shows? We though i would have about 10.5 to 1 with .040 felpro head gasket. We put the crank in yesterday and I haven't measured the deck height for possitive yet. I just remember when i bought the short block the pistons were out of the deck and I tore it down. What do you think, am I in trouble for street. I plan on mixing racing fuel to 91 as needed. thnsks for any reply. walt :toothy7: