Took a break from the floors today and decided to investigate the source of the disturbing grinding noise coming from the back wheels of the car. I was afraid it was from the differential but hoped it might just be in the brake drum. A broken differential would relegate the car back to parts car status. Good used diffs are likely few and far between for a 64 year old car. New repairs likely very expensive.
So its good news and bad news. The good news, the noise was just a loose rivet head inside the brake drum and that differential is just fine. The bad news, the drum was so hard to get off that I cracked a couple of chips out of the flange around the outside of the drum. It won't affect the braking surface and might be "fixable" with JB weld. Also the brake shoes are worn beyond redemption.
I was able to discern the numbers on the diff. Its not the "stump puller" 4.10 ratio. Just the standard 3.90. Seems fairly tight and smooth operating, better than the 52 in fact.
I was also able to fix the left rear door that was originally bolted shut by a previous owner. It just would not stay shut otherwise. I was able to loosen up and adjust the hinges as well as the door catch. Result, the door now opens and shuts as it was meant to.