For all 1968 Cougar trunks to mount the spare tire. Total length according to the MPC is 9.75 inches, with 4 inches of threads on the end. We have found that the overall length is 8 inches with 3-1/4 inches of threads. Basically the same J- bolt as found on 1967 Mercury Cougars but with the thicker, 1/2-13 threads. As we research more we will post our results here. Would love to get specs on J-bolts from those of you with low mile and very original cars.