Ah, the Chief Designer for AMC was Phil Walker, a.k.a. Mr Spacer
Does that tell you anything. ?
I sat down with my rigid 49 Model 18 with a carton of washers, and added washers in various places until everything seemed to line up.
And then cut bored bits of solid to substitute. Out of stainless, so no rust or future ugliness.
This worked well. As a work-in-progress, it took a while. The washers work well until you are sure everything is good.
(Various thicknesses may be needed to fine tune it all.)
P.S. The spacers are listed in the Parts Book.
e.g. under Gear Box fixing bolts (for1949) they have
012999 Spacer on top bolt outside right cost 4 d
but no lengths listed. Whereas the bolts are listed with a size and length.
There is even a pic of it - fat and thick. More are listed !
Yes doing AMC bikes from baskets is a right jigsaw puzzle ...