i need a little 340 help. Lets Talk head gaskets

The chamber on the edelbrock and stock J-heads should be pretty similar shape and would take a 340 piston above deck height, but who knows what the dome on those pistons was designed for. I think I would get a couple of 1/8" spacers and raise the head above the deck and loosely put a couple bolts in. Use some modeling clay in the cylinder to see where, and how much the interference is at TDC. Most of those dome pistons can be shaved down to get clearance and you are probably going to want to do that or change them because you will proably be above that 12.5:1 compression if they are like the old TRW domes. Unless you like running race gas.