Hello, oh Mr tinbum you are not wrong, in the sixties had the 350 and 500. I think that there may be a slight boo boo with the carb. though, the monobloc was much later and it was 60 years ago but I thought they had Amal GP's fitted. Tried a TT on the 350 didnt work very well.
Regret getting rid of them (for peanuts!) but I would have likely as not killed myself.
All the best.
Cheers.
Geoff.