I have run 20/50 motor oil for many years except if I know I'll be in sub-freezing weather for a while. I can't speak to gear oil but when I put house-brand 85/90 in the rear axle a year or so ago I noticed it's more noisy but that could be because it's going gunnysack and I just don't want to admit it. Years ago I used to put 140 in the 2-speeds on our big GMCs in the summer time. Sounds like have the later distributor used up to 1962. I had a problem with my gas gauge where it would register low even when I'd just filled the tank. Then it would go down from there. Eventually it stopped registering at all. After much troubleshooting I figured out that the cork float on the sender had absorbed enough alcohol to get heavy and it sank. I bought a new sending unit that didn't fit but robbed the brass float from it. Problem solved.
