Hey Charlie I went out to the semi trailer to look at the rear end again. Your right, it only has 4 bolts on the housing but five bolt holes on the brake plate. Also 3” tubes that neck down at the carrier.
Thanks for confirming that for me. The rears I have are complete, and in a position of my not being to take any apart. We learn something new every day.
They say any day you learn something new is a day not wasted.