I now have a working car radio with 8-track!
I got the sam's for the quad radio some time ago, and finally stole a couple of hours to properly trouble shoot it....It turned out to be a VERY simple problem. The B+ for the 1st RF amp is fed to it through a tuned coil. That coil, and all other tuned inductors in the AM section connect to the board through a plug. One of the contacts in the plug broke and was open killing B+ to the 1st RF amp....Since the plug is an odd type that would be a pain to try and find a replacement for I bypassed the open pin with a single lead with a plug inline with it. Now the board can be completely unplugged and removed as before and it works properly. I'm almost surprised that I did not find it probing blind...I only removed and reconnected that plug 1-3 dozen times.
Now I just have to find another couple of hours to steal on a warmish day to swap in the new radio.
The auto dimming feature of the high beams seems to be dead, but the foot switch working is good enough for me. Still there is an inline fuse just for the light sensor/amp module that I have not checked yet.