I replaced the body mounts on my BII years ago, the old rubber mounts were soft and ripped the hardware was rusted and broken.
When I replaced them I used urethane mounts and I did one side of the truck at a time
The body ended up 1/2" over to the pass side
I need to loosen them all up and move the body over a little bit
I confirmed with the string that it is not "dog tracking" it is not my wheel alignment or a bent frame, it is indeed the body mounts are slightly off center towards the back of the truck it gets worse
That repair is not high on my list of things to do, I live with it.
Let us know if you are able to center the body on the frame better when you replace your mounts.
I did mine in the driveway with a sawzall and a bunch of floor jacks and pieces of wood....if I was to do it again these days I would do both sides at the same time and lift the whole body off making sure it gets centered when it "lands"
good luck! and good eye
Many trucks from the factory, rangers, explorers come this way with the body off 1/4-1/2" off to one side, it is most obvious over the rear tires or at the rear bumper