they won't be wrong cuz Chevy beds have 4 cross sills, plus the front and back, regardless of length and year, so only 6 holes in the length [actually fleets have 2 holes close together at the front, so 7 there] - why not just get unpunched skids the right length and make holes where you need them to suit your cross sills? .... although the xtra cross sills on a 6' bed sure seems like overkill
Bill