If it's thread you are referring to, I seem to remember that they were 'normal' size, same as Campag etc. However, it was a long time ago that I had one!
Complete guess, but I would have expected Williams to use cycle thread 26 TPI. Most likely is 5 / 16, old front axle, seat lug clamp or lamp bracket boss, just to check the thread.
Resurrection time.
Just found these again lurking in a dark corner of the shed .
I sold the original chain rings a good while back . Going for double set up.
I have some TA OR Simplex rings that should fit . Low geared as well .
Wondering what to fit them on frame wise . Getting limited due to operation down size .
I thought of my Bates B.A.R , but the Canti flex tubing seems to rule out a front changer ?
once you have some miles on the new installation check the tightness of the fixing bolts; some owners report they have a tendency to work loose, a state of affairs which can strip the splines...