As Tim posted above:
http://chevy.oldcarmanualproject.com/parts/1929_54/446.htm
http://chevy.oldcarmanualproject.com/parts/1929_54/447.htm

SGL unit is panel body
Same bumper bracket front and rear on 1/2 ton
Same bumper bracket front and rear on 1 ton

And, as also posted above, 1/2 ton and 1 ton panel body trucks do not have the the same rear bumper brackets as same-sized pickup trucks’ front bumpers.