1967 NASCAR International Stock Car Racing Rule Book NASCAR Grand National Championship Circuit Section 20-3 -- Frames

a. Frames may be reinforced and altered in the interest of safety and to permit the use of 8 1/2 inch wheels, exhaust headers and shock absorbers. But the wheelbase must remain the same as manufactured as referenced by measurements from the front door jam post to the front axle. Unit construction cars must maintain their original body dimensions. Alterations will be permitted in interest of safety. Unit construction cars must maintain minimum ground clearance. Tire wheel base must remain the same as manufacturered as referenced by measurements from the front door jam post to the front axle.

b. Frame modifications are permitted for tire clearance. 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.