That part is called a companion flange. I'm not sure if is reproduced. The corporate Eaton
rear differential was used from 55 first series through 62. It's unlikely there would be any
difference in that component. If it is worn where the seal rides, a speedy sleeve should
solve the problem.
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