1974 NASCAR International Stock Car Racing Rule Book Limited Sportsman and Hobby Divisions Section 20D-23 -- Bumpers

a. Car must have complete set of stock bumpers in top quality condition.

b. No aluminum bumpers allowed.

c. Bumper ends should be fastened to fenders for safety factor.

d. A piece of tubing 1 3/4 inch in diameter may be used to reinforce stock passenger car bumper front and rear, tubing must not be exposed and must remain behind bumper.