Brian Baylis Special - Custom 650C Road Bike Frame/Fork | eBay
Canti mounts, decent clearance, rack mounts. 7mm or so difference in brake block position between 650c and b… could be a go-er. And you’d have a Bayliss, and I for one would look up to you. Even without conversion, you could mount some good rubber on those tires and carve it up. Stunning frameset!