DIY Hotrod Power Steering Pump
First off this can all easily be done in the truck, took me about 30 minutes the first time.
Unscrew the output line, this will also empty the resivoir, so flushing the system at the same time would be a good idea.
Then unscrew the fitting the output line screws into. Here you can see the order of the things coming out, and should go back in. In the picture the pressure relief valve is dissasembled, so it will only be one piece.
To mod the pump, drill the hole through the center of the plug out larger, stock is about .125" if I remember correctly. I drilled mine out to .2" and it made a very noticable difference in the ease of steering. There is also a hole out the side, I drilled another .125" hole on the oposite side. And then as the second picture shows, there is a small hole in the side of the fitting, don't plug it when you drill through the hole it leads too.
There is also a pressure relief valve inside the pump, I would not recommend monkeying with it as it only comes into effect at full lock, or when you can hear the PS pump working hard to turn the wheels. If you still want to adjust the valve, DO NOT shim it. Stock the plug in the valve isn't totally seated, so you can just take it out, clean it up, and then seat the plug. Seating the plug will increase the max pressure. Increasing the pressure only effects the max steering/braking assist. Increasing the pressure unneeded only raises the chance of carnage.
To take apart the valve, here's a handy trick I found, take care not to ruin the machined surfaces!
Here's the plug taken apart, notice the shim in the picture, this shim is not stock, and after testing, would render the pressure relief valve useless.
There is also a screen in the end of the pressure relief valve, if the screen gets plugged, it can cause weak power steering. Even if you arn't going to mod the pump, cleaning the screen is a good idea if the pump is already drained.
And for those curious of the pressure relief valves operation, this is my own personal opinion after staring at it for an hour, could be way off.
When the pressure relief valve relieves pressure from beneath the piston, as the fluid goes through the small tube, there is a pressure loss, once the pressure difference between the top and bottom are 9psi, then the plunger gets pushed down and compresses the spring, opening the big bypass port.