Tom R is absolutely correct, I will just add that GM changed the spare carrier in 51 I believe, making the hole in the rear cross sill useless, but you notice it is still there! Also correct about the center bumper bolt, it is hard to believe GM went to the expense and bother of making a special bolt to fill a hole, but they did. Maybe the hole is there because the same machine to punch the holes was used on the front bumper, and the front used the center hole. Although we all know the front and rear bumpers on pickups are different shapes, so I might be wrong on that theory.
