My 603 is fitted with Jaguar Kent Alloy wheels, these must have had a smaller diameter stud than the Bristol as I remember the previous owner telling me they drilled and re tapped the existing Jaguar nuts, the chrome is a bit tatty on them now so I was going to have a look to see if there is anything that will do the job on the Mister Tee website, link below.
Geoff.
https://www.mistertee.co.uk/