Edelbrock heads on a 340 with KB243 pistons

.027" over the deck? I would seriously consider switching pistons with that build. Get something close to zero deck and run the closed chamber heads. You've already got the heads, the quench would work out much better, and the swapping the pistons at this point would be cheaper/easier than reworking the heads. The fat head gaskets aren't the way I would want to go unless those compression numbers are really what you want.