1966 NASCAR International Rule Book Specifications NASCAR Grand National Championship Circuit Section 20-32 -- Identification

a. Officially issued numbers must be at least eighteen inches high and neatly painted on both sides of the car. A number 36 inches high must be painted on the roof, reading from the driver's side.

b. Numbers on car and division must correspond with car owner's registration card.

c. A positive limit of 32 square inches is imposed on all decals or adhesive-backed emblems supplied by manufacturers for advertising or identification on Competition Touring Sedan race cars. Car sponsors or owners' names are limited to six (6) inches in height. Slogans will not be permitted.