Thanks for the help!
I never would have thought that there was a difference in the "friction" of the washer belt vs. an automotive belt, but after your explanation, it makes perfect sense.
Installed the belts and the machine works like new.
BTW, this is the first repair to the washer since I bought it NEW in 1974!
We like this washer so much that, four years ago, we bought a used one for a friends "camp" that we frequently use.