The wheelbars do have a sheet metal lip that protrudes about 1/4" on each side, but I accounted for that in my 46-1/4" measurement. That number is your actual clearance.
I didn’t realize that the crossbar could be mounted to the rear. I purchased it assembled with the bar in the center. I see that the holes are there though.
I don’t think the locking levers for the casters will interfere. They are outboard on mine.