1974 NASCAR International Stock Car Racing Rule Book NASCAR Grand National Championship Division Section 20-22 -- Roll Bars

a. Steel roll-over bars are compulsory, and must be approved by NASCAR. Aluminum and other soft metals not permitted. Front and rear roll bars must be connected at top (cage type) and bottom on both sides at seat height. Side roll bars are compulsory and must extend into door panels (minimum of 4 on left side and 4 on right side) with additional support on the back of the roll bar. Left door side bars must be convex in shape, with some arch. An additional roll bar must be installed across bottom of dashboard, extending from left roll bar leg to right roll bar leg.

b. Roll bars must be welded, and must be not less than 1 3/4 inches in outside diameter and walls must not be less than .090 inch thick. All welds must have gusset plates, and no less than .090 steel. No pipe fittings allowed. Only round seamless steel tubing permitted.

c. Roll bars must be padded and taped with foam rubber from bottom of left window to center of top in all divisions.

d. For recommended method of installation of roll bars, see diagrams on rear pages of Rule Book.

Note for AeroWarriors.com users - there are three diagrams: here, here and here.