Interesting, I'm surprised that the Weinman 610 works up front. 267 mm is more or less the standard for for racing bikes back in the day. This piece has a good discussion of 650b conversions and has a section on BB height worth reading:

https://www.bikeman.com/blog/guideli...45p4Q5MmEyE9fq

The pedals might be an issue; you might want to look for a narrower platform pedal.

That said, 650b x 42 is sort of the gold medal standard for a 650b conversion; a 38 is also good.