Carb or ignition ?

340Bill said
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 eyes but carb is still **** installing 1906 AVS2 carb this weekend.

I have encountered similar problems and results from not enough initial timing. I would suggest bumping your timing up a little and see if that starts to clean it up I would continue to do that till you reach maximum manifold vacuum then back it off maybe a smidge and see where you're at.