Holley 1920 Idle Speed

What is the recommended idle speed for a slant six 198 with a Holley 1920? It's a 1970 and I have the hot engine idle at about 800 RPM.

When I go out to start the car after having it sit for a day, I pump the gas once start it up and let it idle. I let it idle at about 1100-1200 RPM before kickdown for it to warm up.

Now my question is, a few minutes after starting it, after the engine kicks down to about 800 rpm, I try and back out and go into drive but my engine stalls out. The rpm when I shift into drive is really low, and it's really quiet and it almost sounds as if the engine isn't running at all.

How do I fix this stalling issue? Raise the hot idle? It only really happens when I try and put it in gear after starting it cold.

My Air Cleaner thermostat hose is hooked up, not the big metal hose that comes from the heat riser, could this be causing the issue?

Thanks