Hey Tim, for sure the width of the bed front and inside measurement of the tailgate is 48 1/2" so the cross member will be a few inches wider because of the way it connects to the stake pockets with the 3 bolts on each side............ i will probably have to set up the bed temporarily and see how the cross member then fits and make my adjustments ........ lazy me, I was hoping to avoid all that as I'm a few months away from actually putting the bed on and am painting those parts as it is easier when it is warm and not wintry ........... maybe someone could go to their assembled 46 and provide the number ............ thank you for your extra thought about the frame width etc [btw-the 56 1/4 is probably just barely wider on the AD rear cross member than an original 46 cross member]