Well, it was the injectors. I put on a spare set that was given to me and the stumble and backfire is gone. It is obvious that they were not supplying enough fuel for full load conditions. The duty cycle at idle went down even more from the originals, so there was a definite improvement.

I can crack the throttle to full open and I cannot get it to backfire. Also, the car will pull pretty well from 25 mph in 4th gear (although not very rapidly). So it runs better than it did before. I would say that probably has to do with the failing amm that was in there before.

I do not know about the lack of vacuum advance/retard, but I would not feel bad about buying an ignition ecu if necessary. I know that applying a vacuum to the diaphragm does nothing. At this point I do not feel that it is necessary.

The only question left is: Does the ignition advance or retard on acceleration?
I am referring to the vacuum portion, not "centrifugal".

One other interesting point. I disassembled a bad vacuum advance diaphragm from an old v/c ignition box. It is actually a variable inductance device. Attached is a either a ferrite or powdered iron slug that moves within a core.

I thought that was interesting. A 1000 times more reliable that a variable resistance.

Thanks again for all the input.