Speak to me oh one with info ~ what is this neck down you speak of? I amearly to around 1980 was the change over point . newer style swap in no problems if need be .
and you prob have necked down inner shafts also from the early vintage . there a bit weaker over the newer versions . but if no crazy use there fine or trail spares . and if you want later / newer just swap in no mods .
exactly so does not pertain to my query LOLNothing directly to do with the bearings, it’s just features of the earlier axles.
Any part # avail. for the D60? I remember my D44 loved that kitId get new spindle bearings and seals while your there...

Oh Yeah I forgot about them... looking