I used the late 51-53 width info, board lengths, and groove info on my 53 shortbox. Each board was about, I would say, 1/8 of an inch to wide when I fit it all in the bed because I ended up shaving an 1/8 of an inch off one side of each board. Then redrilling about half of the holes in the rear sill. The boards are tight against the bolts on either side still. That's my first time experience. If I did it again, I would fit all the boards before I cut the grooves. If you do cut yours smaller and then it is too small, please don't blame me. Best of luck.
Colin
