Another carb update. I'm currently running at the following:

Initial Timing: 16 BTDC
Mechanical Advance: 13 degrees
Vacuum Advance: 12 degrees
Idle: 900

I'm all in at 29 BTDC @3,000 with vacuum plugged. This is a little light on a target of 32-34 and I think my idle is a hair high. Having a little stumble off idle unless I load up the accelerator a bit and still some random stumble at low idle cruise.

I read up on transfer slots and their impact on off idle starts and cruise, so I'm going to up my initial timing to 18 BTDC, then lower my idle speed to 800-850, which will take me to 31 all in. This is still conservative but will allow me to adjust my transfer slots more favorably, giving me more fuel/air mixture control, and take away the off idle stumble and low rpm cruise. The additional timing should help as well. I'll stick with the timed vacuum instead of going to manifold at this point.

At least this my current theory without physically removing the carb, which if I'm still not satisfied, will be my next step. I found these two videos on transfer slots helpful:

https://www.youtube.com/watch?v=DpU7pV4Li3A

https://www.youtube.com/watch?v=HS9MHbKLNR0