Mike
Centurians are nice, but they don't have the panache of a Raleigh Super Course, do they? The three wheeler kit I've seen is completely bolt-on. It bolts to the dropouts with a couple of struts running to the chainstays. They used to race them in the UK. I've seen pictures. It involves radical leaning to keep three wheels on the ground. I don't think my mother will be doing any racing, though.