1974 NASCAR International Stock Car Racing Rule Book Modified Division Section 20C-14 -- Frames

a. Frames may be altered for tire clearance and to permit the use of 15-inch wheels, exhaust headers and shock absorbers.

b. Frames may be reinforced.

c. Only approved frames permitted. No homemade box or tubular frames permitted.

d. Any passenger car frame permitted. Length of frame may be altered to allow proper mounting of the body but wheelbase must remain stock for the make and the year model body being used.

e. Front frame snouts may be incorporated into any approved frames. Frame modifications are permitted for tire clearance if similar to original equipment in design, appearance and dimensions. Modifications must be reported to NASCAR Chief Technical Inspector and frame must be approved for safety and workmanship. Any frame rejected by the NASCAR inspector for being unsafe or showing poor workmanship will not be approved until necessary corrections have been made. A piece of channel iron, minimum 4 inches by 1/4 inch, must be installed between the bumper and the rear cross member of the frame by welding to frame rails on each side and bolted with a minimum of four bolts not less than 1/2 inch diameter, evenly spaced between the frame rails. In lieu of channel iron reinforcement, roll bar cage tubing must be extended to rear of frame rails and connected by welding roll bar tubing cross section to extensions. (See diagram on rear pages of Rule Book.)

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