Scream'n 318 ?

I freshened up a 318 some years back and was going to run J heads on it. An old mechanic I know advised against it,said the flat top Pistons and large combustion chambers on the 340 heads would lower compression to "run like a pooch" level. My question is, are there Pistons available for 318 that come above the deck like early 340?? To raise compression?