Need help on combos for 340

Low side...
http://www.carcraft.com/techarticles/ccrp_1006_small_block_mopar_stroker_dyno_test/index.html

There are some tweeks that can be made to that build and get over 500. That engine with a 950hp and electric water pump drive made right at 500 on his dyno.

High side you'll need to spend some money on cylinder heads and a big cam, compression to get 600hp

11:1
Light bobweight set up
260-270 at .050 cam .650 lift roller or solid
Victor intake
950-1050 carb
Heads that flow in the 300+ range
1 3/4" or larger headers