Well, I had a nice long drive in the Imperial today. I think I have all of the bugs out of it (that I'm going to worry about) for now. I ended up leaving the vacuum advance disconnected and plugged, and except for a small amount of detonation/pinging just before the downshift at 'foot to the floor' punching it, it starts and drives very well. I'm guessing the centrifugal advance is all it needs.
For those of you who might do a 4bbl conversion on your cars, I obtained the correct 4bbl kick-down lever that attaches to the throttle lever and pivot at the rear of the motor, and ended up adjusting the linkage (at the trans lever adjuster - the only one I have) forward almost half an inch on the rod end.
My shift points before the adjustment were 1/2 @ 35 and 2/3 at around 50. Then the torque converter would immediately lock up...so, not good. With my adjustment it now shifts 1/2 @ 25 (+/-) and 2/3 @ 35 (+/-) and the lockup kicks on when it should @ 45 mph.