This information taken from the 1958 parts book: Group 5.420 Axle Shaft
55-56 Pass.--left (17splines-28 13/16 O.L.) pt# 3714781
55-56 Pass--right(17 spline- 30 5/16 O.L.) pt#3714782
57 Pass,corv.(exc.P/Trac.)-- left (17 splines 28 11/16 O.L.) pt#3739107
57 Pass,corv.(exc.P/trac)-- right (17 splines 30 3/16 O.O.) pt# 3739108
51-58 1/2 ton-- right(17 splines 29 5/8 O.L.) pt.#3694769
51-58 1/2 ton-- left(17 splines 30 5/8 O.L.) pt#3694770
No mention is made about axle diameter but the bearings are listed different.
5.855- rear axle bearings
55-56 pass.- ball bearing assy. (ND-rw507bsy-18c) pt.# 3729375
57 pass-ballbearing assy.(stamped 904262) pt.#904278
33-36 pass,comm.(exc. cc,dc,ec,fc)
37-39 comm.
40-58 1/2 ton--race assy,outer, w/roller (HY OR 1502) pt.#no 111121
DANDYD