The 3100 and 3800 share the same splash apron behind the bumper
All sheet metal parts are shared cab forward
The bumper itself is just thicker and the bumper spring to frame mount is different but that’s all hidden under the apron which connects with 4 of the bumper bolts.
The curvature of the 1/2 to the 1 ton is the same
You need to go bigger to 1.5 ton to get the larger steel bumper and larger apron
The apron might connect onto all 5 bumper bolts I think there is a flang for the center bolt.
source:
Parts and Accessories Catalog P&A 30 March 1957
Group: 1.287 PANEL, Radiator Grille Filler
1947-53 ALL COMM.* (exc. DD**) 3684145
*ALL COMM. = 1/2, 3/4 and 1 TON TRUCK
** DD = (Dubl--Duti)(Forward Control Delivery Chassis)
