Wheel rim widths - '56 swing arm Flash

[Jules]

Hi all, just been reading the latest posts about wheel alignment vs frame alignment and prompted me to get out my wheels and check mine now that the steering head is done. There old tyres on the bike were 3.25x19 and 4.00x19, whereas I know the spec is 3.25 and 3.5, but they were both worn out anyway so they have been scrapped. BUT when I put the wheels together (without tyres) the front wheel actually looked wider than the rear, the trusty vernier confirms it too, there is 1-2mm difference in overall width and also inside width where the tyre seats. Sizes are around 47mm inside and 67mm outside, and it seems to be in the "rollover" shape where the tyre fits into - one has "softer" (larger) rollover radius. Both front and rear have full width alloy brake hubs......
Any thoughts on the wheels, anybody seen it before? they appear original (ie I've had the bike in pieces for 30 years and it had been badly bush bashed prior to me).
Also, Muskrat referred to making sure the wheels are central in the frame/front forks in the prior post about a plunger frame, does this same comment apply to swinging arm? if so, central to the swinging arm or central to the frame (because my swinging arm is not central in the frame, nor is a few other bikes I've looked at after I'd had my frame straightened........ )
cheers

[muskrat]

G'day Jules.
Both rims should be WM2 = 1.85". The shapes varied with different manufactures. Part # for 56-57 = 42-5637. I'd say their not original.
My '57 (same hubs) wheel is central in the swing arm which is central to the frame. Not sure on other years but would think it odd.
Cheers

[Jules]

thanks Muskrat, 1.85" =47mm so I guess thats the tyre seat (inside) dimension and fits my measurements,so the rollover radius looks to to be the difference. So, as you say, looks like one may be original the other a pattern.........
bit puzzled by the swing arm position because the frame has been straightened in Melbourne (years ago mind you) by the very well recognised guy in Ferntree Gully (name escapes me right now  ), and I've looked at a few other frames/bikes and they were a bit to one side too, so assumed that this was another BSA build "quirk" (bit like some Harleys apparently too!).
Thanks for the feedback I'll assemble everything and string line it allowing for the difference in overall wheel rim width and see how I go. I suspect I'll have to have a go at adjusting the wheel rim centreing via the spokes as you suggested to me in an earlier post when I had put the front wheel into the forks and found it offset  , cheers