The picture of the front bumper in the 1947/48 KF Parts manual shows 4 long bolts, part no. 202884 which go through the bumper guards (hence, need to be longer) and two short bolts for the corners of the bumper which do not go through the guards, they simply fasten the bumper. The two short ones are part no. 202883.
The rear bumper uses the same except only two of the long ones through the guards.
