So I had similar issue with mine, 72 340 thumper cam/LT/stall/ Holley knock off 750cfm double pumper/Edlebrock heads and air gap intake/MSD blaster 2 coil. adjusted timing to 15deg initial 30deg all in. new plugs gapped at 42, adjusted carb to roughly 14" vacuum plus 1/4 turn..no more burning...