Fred - Seems you've found what some folks call the predecessor to the T-5. It's actually a Borg Warner T-50 5 speed OD transmission. See the snapshot below for some generic info on the transmission. I actually drove a late '70s Chevy Monza with this 5 speed. It was well suited for that little thing, but I have my doubts about use in a truck. It's also hard to find parts for if it needs repairs/rebuilding IIRC.

Here's a link to an old article by some folks that have a lot of info on T-5s also online.
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~ Dan
1951 Chevy 3 window 3100
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"My Grandpa Carl's Truck and How it Became Mine"
1966 Chevelle (Wife's Hot Rod) | 2013 Chevy Silverado (Current daily driver)
US Army MSG Retired (1977-1998) | Com Fac Maint Lead Tech Retired (1998-2021)