Yes, the rim size is 6Jx16.
The regulations for one of the hillclimb championships that I'm competing in states that my tyres must be 55 profile or higher, unless lower profile tyres were fitted to the model as standard or as a manufacturer option. The onus of proof lies with the competitor.
Ideally I would like something along the lines of an old SEAT Cordoba
brochure that shows the tyres sizes so that I can show it to a scrutineer if challenged. If anyone can scan the relevant page from an old
brochure or sell me one, it would be much appreciated.