You may also try to find a Saganaw 3 speed which was available on later cars & trucks. They are full syncro units and can be identified by the 7 bolt side cover. You will need to do some modifications to the shift arms and change the front drive shaft yoke. They are good transmissions and seem to be more available and reasonably priced.
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