Could be many things. I also have a 12V Bomber truck. I had similar issues and just replaced the steering box with a new box from Borgeson
and it fixed the problem I was having and improved the steering 100%.
If you are really nuts here is what my Klineman Service Manual says:
PUMP FLOW RATE AND PRESSURE
The following procedure is used to test the operation of the power steering system on the vehicle. This test will provide the flow rate of the power steering pump along with the maximum relief pressure. Perform test any time a power steering system problem is present. This test will determine if the power steering pump or power steering gear is not functioning properly. The following pressure and flow test is performed using Power Steering Analyzer Tool kit 6815 Pressure Test Gauge and Adapter Kit 6893.
POWER STEERING ANALYZER INSTALLATION
WITHOUT HYDRAULIC BOOSTER
Remove the high pressure hose from the power steering pump.
Connect Tube 6844 into the pump hose fitting.
Connect pressure gauge hose from the Power Steering Analyzer to Tube 6844.
Connect Adapter 6826 to Power Steering Analyzer test valve end.
Connect the power steering hose from the steering gear to Adapter 6826.
WITH HYDRAULIC BOOSTER
Remove high pressure hose which goes to the steering gear from the tube coming out of the booster.
Connect Adapter 6826 to the Power Steering Analyzer pressure gauge hose.
Connect pressure gauge hose to the tube coming out of the booster.
Connect Tube 6844 to the steering gear hose and Power Steering Analyzer test valve end.
FLOW AND PRESSURE TEST
Check belt condition and tension.
Open the test valve completely.
Start engine and let idle long enough to circulate power steering fluid through flow/pressure test gauge and to get air out of the fluid. Then shut off engine.
Check fluid level, add fluid as necessary. Start engine again and let idle.
Gauge should read below 1034 kPa (150 psi), if above, inspect the hoses for restrictions and repair as necessary. The initial pressure reading should be in the range of 345-552 kPa (50-80 psi)
Increase the engine speed to 1500 RPM and read the flow meter. If the flow rate (GPM) is below specification (Refer to pump specification chart for GPM) the pump should be replaced
CAUTION: The following test procedure involves testing maximum pump pressure output and flow control valve operation. Do not leave valve closed for more than three seconds as the pump could be damaged.
Close valve fully three times and record highest pressure indicated each time. All three readings must be above specifications and within 345 kPa (50 psi) of each other.
Pressures above specifications but not within 345 kPa (50 psi) of each other, replace pump.
Pressures within 345 kPa (50 psi) of each other but below specifications, replace pump.
Open the test valve and turn the steering wheel to the extreme left and right positions three times against the stops. Record the highest pressure reading at each position. Compare the readings to the pump specifications chart. If pressures readings are not within 50 psi of each other, the gear is leaking internally and must be repaired
CAUTION: Do not force the pump to operate against the stops for more than 2 to 3 seconds at a time because, pump damage will result.
ENGINE RELIEF PRESSURE (P.S.I.) FLOW (G.P.M.) at 1500 RPM
3.9L 1400 to 1500 2.7 to 3.1
5.2L 1400 to 1500 2.7 to 3.1
5.9L 1400 to 1500 2.7 to 3.1
8.0L 1400 to 1500 2.7 to 3.1
5.9L Diesel 1450 to 1550 3.1 to 3.5
All With Hydraulic Booster 1450 to 1550 3.1 to 3.5
NOTE: After preforming test and removing Power Steering Analyzer, check power steering fluid level.
All the part #'s listed are from the Chrysler Service Department