20 years wondering no more

I may be wrong on the gear ratio, am I missing something though? Did mopar not have a 4:10 gear ratio? I know I am running the chevy 4:11 Richmond set up in our 400bb duster. But just doing a quick research on the Web shows there being a 4:10 sure grip as an option in these years for the 8 3/4. I may be wrong, and if so my apologies. And as I did state before, it has been 20+ years and probably 20,000+ beers ago. So it's possible my memory is fuzzy.