1918 Sidecar alignment question

[spandau]

I have a 1918 J model with a sidecar. However, the sidecar does not fit properly on the frame. I’m guessing that the sidecar frame may be a later model, because it is a couple inches two wide between the two lower mounting points. This has been “corrected” by mounting to a different point on rear of the bike (further back) but it’s really not aligned properly.

The distance between the two lower mounts (on the sidecar) is about 42”. Can anyone verify if an earlier (1918) sidecar frame would be a shorter distance? Is there a structural difference in later models? I’m trying to determine what to look for if I can find another sidecar frame.

Thanks,
Steve