Originally Posted by
Bill Kapaun
IF your FDER will move an additional 2+mm toward the smallest ring, a 122.5 would work. Other option is a 127mm, but your FDER would need an additional 3mm of outward travel.
Do a bit of homework and you don't have to swap a crank.
UN-26 is probably adequate, but I don't begrudge a UN-55.
Undoubtedly the 124mm BB in the OP's bike is not original to the bike as it would have been a cup & cone unit. This leads me to believe that there is some room to play on spindle length and see if a commonly available length would clear chainrings and FD reach (both in & out). Yes a bit of homework and measuring would likely answer those questions.