Recently I went to change out my driveshaft nuts and bolts when it struck me, what year did toyota change driveshaft bolt diameter? Was it the middle of 1968 with all of the other changes that went on? Anyone have a part number for the driveshaft hardware that would have came on a 1968? Fj55 if it makes any difference. They have a 12mm head instead of the 14mm, and a much smaller shoulder diameter than later driveshaft bolts.