[SCOTI]

I used existing holes @ the very rear of the frame as the starting point to locate everything. I installed bolts in these holes & clamped the opposite ends of the hitch in place w/vise-grips to make sure everything was square & cleared.

Using the holes @ the end of the frame rails, the 'edge' of the hitch flange was .500" from the edge of the frame. I made sure both sides were equal before drilling any holes.

The holes in the frame that I used to determine where to locate & drill the 'new' holes in the hitch flange were just under .500" diameter. So I drilled the flange first; squared & bolted in the hitch (end of frame rails), clamped the opposite ends of the hitch in place, then drilled the hole out in the frame using the flange hole as the guide. One side was exact, the other had to be filed just a bit. It's definitely close enough for GOV work.