Slant 6- Idle and Running

sounds like you may just want to start with a known good carb, many here. Heck I got one if you want to come over this week and pick it up to try. 5/55 Fwy Tustin. Could be a hot vacuum leak? Pinch off all the vacuum lines including the advance and let it warm up. see if it will drop off choke onto base idle and idle. Hmmm, you said it will idle with the choke actuated slightly.....?