Most vendors will have the saddles to mount your new rear end. Classic Parts lists a complete "Rear axle conversion kit" including mounts, u-bolts and shock mounts part number 93-311 that will work for a 55 first series

1954 Chevy 1300 engine 235 (1959)
1955 (first series) Chevy 3100 engine 261 (1957)
1927 (other brand) Model T- engine 327 (1968)