Second and third gears were synchronized in that series transmission. It is known as an SM318 which was also the designation for the later open driveline unit. Most parts don't interchange with the later version, however.
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