mrv 

- I will take a few measurements.
I picked up a set of 700c wheels w/ Paul hubs for a very nice price (along with a bunch of other stuff I needed: tires, crankset, bars, fenders, rack). I'm going to stick the MAFAC Racers on the bike temporarily, I hope, while I learned to be a dirty fixie rider. (and I got a whole road bike project going also, The Allez Castrophe')

I'll take a best-guesstimate on the 650b rim location and see if 73mm would reach. I think it's be close. I did a quick & dirty measurement with a set of Shimano caliper brakes (shortish reach) and it was "about" 55~60mm straight down from the brake pivot bolt. (Shimanos were toooo short.) So another 19mm should be all I need to reach w/ 650b wheels.....
...but I still got the annoyance of deflating tires to remove / install. In the pic below are 700c X 400mm tyres.


Still in Phase-0 of Bike Launch
- Phase 1: something ride-able, safe enough to be traffic
- Phase 1.5: strip paint; braze on previously described bits (pray I did a good enough job); repaint; framesaver
- Phase 2: Paul Motolite brakeset - for the $386 experiment: Will Paul Motolites work with 700c wheels using brazed on posts for 650b ?!?! (entirely possible I never mention this foolishness again, but not probable)
- Phase 3: 650b Wheelset; 4 spd IGH w/ DT shifter; matching Sturmy-Archer hubs (man, a lot of the S-A stuff is hard to find for sale on line. Mostly just the silver or black. The cool anodized stuff is a bit of a unicorn.)
Last phases are lots of cash. So not sure on timing. Once phase 1 is done, there may be some bikes popping up for sale to thin things out.

cheers.