Sounds like you have a 360 stroke crank with a 340 compression height piston.

A 340 with standard ch pistons should not stick out .100 on a 9.53 block. That is only .050" shorter than stock.

What is the CH on the new pistons? 3.31 stroke divide by 2, 1.655". Add that to your rod length, should be 6.123", 7.778". Subtract this number from you deck height. That will be the tallest ch you can use.

Career best 8.02 @ 169 at 3050# and 10" tires small block power.