Your Tail Shaft Extension number is 3707195 and the case number 3845122 were used on 3-speed Cars, Corvette's and Trucks from 1955-59, as Fred said...very common.
You got the date code right...
Mike B
Mike Boteler
1956 Chevy 3100 Resto Rod 1952 Willys M38 Army Jeep 1983 Jeep CJ7 Laredo 1984 Jeep CJ7 +++++ Silver Spring, MD
