these were the exact sizes UVA used to fit to the fugs.....as fitted to mine and Pauls, and god knows how many other fugs, I actually quite like mine!.......5-spoke wellers actually very rare now, this is the first set I have ever seen for sale. although a ton is a bit steep, but they do come with good-ish tyres

http://cgi.ebay.co.uk/BEACH-BUGGY-BAJA-SET...1QQcmdZViewItem