It is a pretty simple design. It is all 2"x2"x1/8" angle iron. There are two vertical pieces. I drilled a 3/4" hole in them. They connect through the gate bolt holes. I have not decided if I will use 3/4" screws or 3/4" hitch pins yet. Welded between them is a cross beam. I had to remove the light for the license plate. I'll snip those wires and terminate them since I won't be using a regular plate. The rollers are just sitting on the cross beam in this picture in the approximate locations where they will go. I was just checking the height to make sure the rollers about about 1/4" or so above the trailer bed. It is hard to see in the picture, but I did drill 1 1/8" holes in the crossbeam where it covers the brake lights. That was the largest step bit I had. Since there are also break lights on the side, it doesn't concern me. The bracket is held in place with the original gate bolts in this picture which are too long for the bracket.
After this picture was taken, I mounted the mini-license plate on the back of the wheel well. I drilled the holes to secure the rollers to the bracket. I also eased all the sharp edges on the bracket. I'm now in the process of painting the bracket.