[Jayce]

Both radios I have use the 35C5, I can tell that much on the faded label on the currently functional unit. Sadly, the model number is not only faded, but someone inked in: T1240A and the Sams manual number over that area, so I can't make out anything. I know the one unit is definitely a T1243B as the label on it is great. I am suspecting the working radio might be a T1243A as it definitely shows signs of being a bit earlier in design. The T1243B has a dial light and there is a change in the controls as well. It has a Hi-Low tone switch where the Off-On for the FM-AFC is on working radio and the band switch is marked: AM FM-AFC instead of just AM-FM.
You might be on to something about the 50C5 swap. I am suspecting that though it tests well, there might be something wrong with the 50C5 I tried. I tried that same tube in both radios in place of the 35C5 and it just made them hum badly and play poorly. Note: These were two recapped radios that were playing fine beforehand and played fine when I put the 35C5's back in.