Well it looks like at least for 1968 its 12mo 12000 mi (12k).
That doggone hemi.
I will search for some other years.
All the more reason to go to a 42-class model year & transmission format for PSMCD like I laid out below.
Still no need for any "factoring".
Great link, just looking at the updates.
I like the 10.8 CR 390/300 for 1963. Sure.
Still hunting for more hemi warranties.
1967 Hemi, same, 12m 12k