That was the year that they went to an open driveline in both series. I can't imagine they made a 1/2 year only set up. It should be a 3:90 ratio or possibly a 4:10 if it had an OD. The 55 1'st series that I have seen look the same as my 56.
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