[Mike C]

8.75" if it is a 12 bolt truck. With GM numbers on the ring gear, that would be my guess.

I have never had a problem just going to the parts store and asking for a seal for the vehicle. But the date on that Ring gear, if it is 1 of 67 would not have been found in a '68. Have the parts guy look up the seal for a '67 12 bolt. I would not have thought them to be different, but you never know.