I installed the URB's front and rear, one each. On the front there are three holes with captured nuts. I had not noticed that before. The front two hold the ARB Bumper. The rear one was unused. So using the thick washer that URB comes with as a spacer (it matches the ARB metal thickness) I mounted the URB in the rear and center frame locations, locating the URB about 2 inches further back, improving approach angle even more. I then ran a bolt in the front hole to secure the ARB. This would not be an ideal hook up location in water or mud, but for our type of wheeling it should be fine.
At the back of the truck the URB bolt was, as Stan predicted and said Shawn at Jonesy's had supplied some longer bolts for, with my factory hitch, was too short. Its a combination of the thicker URB washer and slightly shorter bolt. I had already replaced these bolts a few years ago due to rust (check yours) so I had good longer ones on hand to use.
This also got me thinking about the washers: Why use a thick washer with an internal diameter hole the same size as the 1/2" thick steel I was clamping. I'd already put them on the rear so I left it, but I omitted them in the front. Some web research suggests there is no reason and in fact downside to using a lock and flat washer in the same application (you lock to the bolt head or nut and to a flat washer that can slide on the clamped surface), and no reason at all to use a flat washer with an internal diameter hole the same as the 1/2" thick steel I was clamping. If the clamped material was thin and I wanted a larger clamping surface area or the material hole was larger diameter an I wanted to span it, then ye, a flat washer makes sense. http://www.boltscience.com/pages/faq.htm#11