Beater79TA

Looking to upgrade to aftermarket rear brakes and need a measurement. Does anyone know the thickness of the backing plate for a 9 bolt disc brake rear? The measurement needs to be at the center of the backing plate where it bolts to the axle and not the edges. I need to know the axle offset to order the correct offset for the new backing plate and don't want to disassemble the axle to take off the backing plate to measure the axle offset from the axle housing end.