I measured my mounting bolts drivers side front to back. I put the bed boards on the cross sills marked them and then drilled them. The offset washer I used a forstner bit to cut a nice flat bottom. I put the boards in my Bridgeport, so I could line up and hold the counter sink where I needed. If you drill the 1/2” hole first you will not be able to hold the forstner bit because the point will be in the bolt hole. I would lay the bolt holes out, line up the offset washer and mark it, then drill the countersink, then put the washer in and mark the bolt hole. I had to do that with my rear bolts because my bed was already in my truck before I put the rear bolt in. The pictures are in order front two and rear two bolts and the bolt look to be 1 1/4 from the groove.
