pretty easy to miss the question gaz!
lemme see if I can find it .... you're makin a "custom" bed, so it can't much matter what it started out as .... you must know whether it's a stepside or fleetside .... if you made it a "custom" length then long or short don't matter .... so the list of measurements must be what you're askin about .... so you're trying to figure out which new strips to get for your "custom" application?
wouldn't the hole position be determined by the frame you're putting it on, and the number/position of the cross sills? and Mar-K didn't tell you Chevy beds don't have 8 cross sills?
more info on what the bed is for might help
Bill