I've been running HA for a few years. Drilled my own box and used the Redneck ram kit. Stock '86 pump w/ restrictor drilled out, using synthetic ATF and I enlarged my stock reservoir. I haven't had any problems except for the early style ram leaking, but they replaced it with the new one.

I don't think the pressure is nearly as important as the flow, and that is the primary difference between stock and aftermarket pumps. At idle, coasting and steering quickly into a parking spot or something, I can outsteer my pump. Other than that, its not usually noticable.

You can easily figure out what the working pressure they used is if you know the piston/rod diameters.

I think little or no fluid flows through the lines except when steering assist is needed. Most of the time the pump is bypassing internally. PBB has an extremely thorough writeup by Billavista in the tech section.

And FWIW, I have heard of people having problems with the v6 pumps.