I just found this document from
https://www.gmheritagecenter.com/doc...olet-Truck.pdf
and apparently the stock setup from Chevy in 1979 for the 454 dually was a 3.73 rear diff, with 4.10 and 4.56 being options...
... and that is with the Camper Special 10,000 GVW...
... with a non Camper Special they came stock with 3.21 diff gear ratio.
I guess they thought it could still handle to 10,000 GVW total weight with the 3.73...
... though that is more about weight in the bed than pulling a trailer.
Any thoughts on the difference in carrying 2 tons verses towing 3 or 4 or more tons with regards to diff gears or overdrive transmissions?
Thanks