more slant problems

Sounds exactly like my 69 Slant Six w/ Holley 1920. Idled like that for 18 years, driving me crazy. Always wanted to die when you shift from N to D and idled smoother with the choke plate held down. Wasn't timing, though it idled better w/ a lot of advance (20 deg?). After ~3 carbs plus rebuilds, valve jobs, even a new long block (wasn't compression!), I finally got another Holley 1920. It then magically ran like a dream. I think those are the classic signs of running lean and it seems there are a lot of bad Holley 1920's out there and poor rebuild shops. Not sure why the last carb was so much better. Car was stolen a few months after that.