A 1950 3 speed is a 318. A 319 is a 55 to 65 overdrive. GM did a good job of confusing the issue. 48 through 54 3 speeds are called
SM318's as well as the 55 through 67 open driveline transmissions even though they are nothing alike.
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