Does it have the 4 bolt side cover? If it has the long tail shaft (22" overall) it could be from a 55-61 truck or 55-57 car.
If it has the short tail shaft (17" overall) it could be from a 62-67 truck or 58-67 car. There is a date code on the tail housing along with some casting numbers. A date code like: A 15 0 would be Jan 15, 1960. There are some minor differences between car and truck transmissions such as the side cover and the lower mounting holes. 6 cyl and V-8 transmissions were the same in that era.
Fred


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