KC, I think your information about finding a more modern rear with better gearing will be WAY easier than trying to find gears that haven't been made for 50 years.
The Isuzu NPR or NRR might be a good place to start looking.
Mike B
Mike Boteler
1956 Chevy 3100 Resto Rod 1952 Willys M38 Army Jeep 1983 Jeep CJ7 Laredo 1984 Jeep CJ7 +++++ Silver Spring, MD