hello 54 dd. just measured the locations of the cross bars on my 55 first series short box. using the corresponding strip bolt heads,, from the centers,[REARMOST BOLT MEASURING FORWARD],from the first bar,, the second bar is 22 3/4 in.,,,the third bar is 26 3/4 in. from the second,, and the fourth bar [most forward] is 24 1/8 in. from the third. be careful if you locate the bars using the holes in the strips as some of the holes do not correspond to the cross bars. some of the bolts just use washers and nuts on the bottom side. hope this helps.
