This car was supposed to race on Firestone Tires due to a sponsorship deal that Bruce McLaren had with Firestone. Once they started racing they found that the Firestone tires were wearing out very quickly which was translating into much to frequent pit stops. They switched to the Goodyear Tires that the rest of the Shelby American cars were running - Shelby being among other things a Goodyear dealer.

So the wheels might actually be right - for the very beginning of the race (I'd have to check race photos) but if they are it is the tires that are wrong.