I have a plan to do a 650b conversion... I just need to find the right frame. Also I would love to find a set of vintage rims (or wheels) for the project. The vintage stuff is just so hard to get in the states. Velo orange sells a new set of rims for around $150... perfect for a daily rider and to see what frames might work for a conversion.

Brakes are another issue... I want to use centerpulls and I think MAFAC will work, but that depends on the frame also.

The OP's conversion looks great... it seems the bike was made for it!