Had a look at mine. It does not have the 5/16 nut and bolt as shown in the pic. above. It has a 1/4 self tapping screw installed. Hole is to small for the 5/16 bolt. A variation?
69 Z/28 Dover White X33,ZL2,PS,M20,Std.int.04C
67 SS/RS Mt. Green 1W,2LGSR,3SL,4K,5BY,07C
70 Nova L78 Blk. Cherry,Sandalwood,M21,02B