It was quite common to install modified Borg Warner overdrive units and others
in various torque tube vehicles in the bygone era. There is a publication from Tom Brownell
"How to restore your chevy pickup" that has some information on the system.
In my opinion the machining costs would far exceed the gain unless you had a shop with
all the tooling and welding equipment.
Fred


1956 3100 Pickup/Red/350/3sp OD/PS/Disc Brakes
1957 Bel Air Sport Coupe/Red/355/TH350/PS/Disc Brakes
2017 Silverado LT Single Cab SB/Black/5.3/6 Speed Trans
1947 Willys CJ2A w/F-Head engine