Without more specifics it is hard to prove for sure, but from what Chris has provided so far, I believe you are correct.
From what I can tell, the current standard for E2 axles is a Spring Center(SC) measurement of 50.50”. This is the measurement from the center of each of the centering holes located on the axle spring perches, across each axle (see my axle sticker below). I do not know of Oliver manufactures the steel suspension frame to which the spring/axle assemblies are then bolted to the aluminum frame or if this component is provided as part of a complete suspension package provided by Dexter which is bolted to the aluminum frame. Regardless, it appears that there was a period of manufacturing where the axle SC measurement was less than 50.50”, necessitating that the spring hangers on the steel frame were moved inboard. Not a defect IMHO, rather a manufacturing change to meet the narrowed spring perches being provided on the axles at that time
Couple of questions I have:
1) how many trailers were manufactured with these narrower spring perch mounts?
2) since the steel suspension frames are bolted to the aluminum frames, is it possible for those impacted hull#s to have the narrower steel suspension frame replaced with one with a SC of 50.50”, thereby allowing newer axles to be fitted?
For those interested, HF (hub face) measurement of 68.75” (as shown on the sticker) is the outside to outside width of the axle, as measured by the outside of one hub, across the axle, to the outside of the hub on the other side. I believe that this should remain unchanged for all E2 trailers built.