Re: Rims for 1948 RRA
I think the rims/tyres should be 26 x 1-3/8" if you're going to use 26", not 26 x 1-1/4".
For the brake drop, I measured the following rim outer diameters which should help:
26 x 1-3/8: 603mm
27 x 1-1/4: 641mm
700c: 633mm
Tubular: 633mm
With old brakes, it's not 700c which is the problem, it's more likely whether there's enough drop to reach the 26" rim. Usually it's the skinny tyres chosen for 700c which look out of place.