440 Help Needed

I guess I should have been more specific.
“Known good” for the application at hand.
A known good 1bbl off a slant six might run great on a stock 225, but isn’t going to work on your 440.

Lumpy cams that produce lower vacuum are often problematic for carbs not calibrated for that situation.
Add exhaust manifolds into the mix, and the idle mixture gets diluted with residual exhaust, exasperating the issue.

Part of why I have a variety of carbs is to have something that’s both “known good”, and a good match for the application.

If you have a friend with a similarly set up engine to yours, that’s not having those idle issues........ maybe they’d let you try their carb on your engine.
Or, try you carb on their engine and see if the motor is still happy.