If you have a Chinese repop fuel pump it's likely that the fuel pressure is high. One I had would run OK but when I shut it off and let it sit for a few minutes it would flood. Put out 7 PSI.

When you overhauled the carb, did you check the float drop? I found one that had so much drop that the needle would hang up because the float would try to push it sideways. It would flood till you banged on the carb with a wrench. After a while with heavy load it would do it again. Does the float float? Did you check it for leaks by shaking it by your ear to listen for sloshing? Is it plastic? I've seen alcohol permeate them till they sink. Cork too.

As for misfiring on two cylinders, I'd check for gas fouled plugs (Black).

1951 3800 1-ton
"Earning its keep from the get-go"
In the DITY Gallery
1962 261 (w/cam, Fenton headers, 2 carbs, MSD ign.), SM420 & Brown-Lipe 6231A 3spd aux. trans, stock axles & brakes. Owned since 1971.