I take it you've test fit some 650b x 38's? If so, why not? Typically, however old Italian racing bikes won't make the fit unless they're early70's or older vintage.
The first 650b conversion I did for someone else was a
'61 Bianchi Specialissima.
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If someone tells you that you have enough bicycles and you don't need any more, stop talking to them. You don't need that kind of negativity in your life.