Yes Keith the nuts are standard.
I believe that the footrest retaining stud is part number 42-4855 and if I remember correctly it is a 1/2inch diameter round threaded with 1/2" cycle thread (20TPI) both ends. I also seem to remember that it has a nut brazed onto one end.
The other end has a plain washer and a locking washer with a nut (part number 2-124). I have a list of standard nuts that BSA used and part number 2-124 shows it as being a 1/2inch CEI X 20TPI nut, 0.203 inch thick and 0.782 inch across the flats.
So what you have appears to be correct.
Oh yes, FYI:- the stud type bolt, for want of a description, should be 11 3/4 inches long....anyway, that's the information I have. Hope it helps.
Beezageezauk.