The bumper is a separate issue. I would think that a 3/4 Ton has bumper supports much like a 1/2 Ton. Check to see if the frame is at the same height on both sides. Usually these old trucks have springs that don't sit exactly the same side to side.
There is a procedure in the manual for setting the back of the hood. If you followed this exactly and it didn't last, something is worn, most likely your hinges.
The entire front clip is adjustable. It pivots or rests on a central support under the rad at the front. You should loosen all the bolts and then use the support rods under the hood to draw the sheet metal into place. The rad saddle support should be very loose while this is done. When you have the right height, the support needs to be shimmed as required. No other shims are used.
