If you are after a 4.10 ratio, the most consistent tale is that they existed in the years 67 to 72 on 3/4 Ton trucks with automatics. Now, I have also been told that the truck should have coil springs. Apparently for some of the years there were trucks with leaf springs and I believe Dana rearends. It is always possible that an optional ratio might have been installed at the factory, or there after. The 4.10 crown gear has 41 teeth.
