I was too young to ever tow with it but my grandparents had the srw version of what you are looking at. They lived in Washington state and towed all over, Canadian Rockies, Yellowstone, down to Arizona.
This is a bad pic but you can see the truck in the lower left photo and sort of in the one about it. Two different 5ers.
We were usually following them with our suburban and tt, which you can sort of see in the one photo.
That was back when people didn't expect to go 70 up steep mtn passes.
I don't know for sure what year their pickup was, but I'm pretty sure it was the first year for that body style.