Alvin,
I did what you said and the guy at Eaton was indeed very helpful. He knew without having to look it up that the "free arch" for a 37 1/2 ton was 2” on the front and 6 ½” on the rear. I passed that on to the shop that has my truck...couldn't talk to the tech at the time but I hope it's what he needed.
Thanks,
Mike