1977 NASCAR International Stock Car Racing Rule Book NASCAR Grand National ® Championship Division Section 20-13 -- Drive Shaft

a. Drive shaft and universals must be similar in design to standard production type.

b. It is mandatory that two oval (360 degree) shaped brackets, no less than 2 inches wide and 1/4 inch thick, be placed around the drive shaft and fastened to the floor or cross member of the car to prevent drive shaft from becoming dislodged and dropping to race track.