by JerrryR » Fri Dec 21, 2018 2:04 pm
The 67XLHs used the 667 belly prefix. I think the initial logic was it was a different motor. What is interesting is it appears in 68 they went back to the 768 prefix. I am unclear if it was a running change in 67 or a model year change in 68? Starting in the early 60s HD went to even VIN first numbers in even years and odd numbered VIN first numbers in odd years. I think Dave has a write up about this on the website, if not I'm sure someone will jump in with what year it started or if I have any of this wrong.