My 4.3L has about 55psi at a steady idle. If I goose the throttle I see it jump to about 60psi. This is after I replaced the fuel pump and the regulator with new parts. The pressure stays over 50psi for a while after I shut it off.
I thought I'd mention that my truck would "buck & jerk" pretty bad under load on days with a lot of humidity(rain or fog) recently. After it sat for a little while after a good warm up it didn't do it nearly as bad. It seemed that there was moisture in the distributor cap that caused a misfire, and after it sat after being warmed up, it dried out the moisture somewhat, and ran ok, or at least a lot better. On dry days it didn't do it.
I had changed out the distributor cap about 2-3 years ago, and didn't think that would be a problem. The cap is the kind that have built in circuits that transfer some of the terminals from one side to the other. I believe that's just asking for a crossfire/misfire.
I removed the cap and saw a lot of corrosion(white chalky crap) on the terminals,(zinc not brass) and even on the screws that secure the rotor. I replaced the cap and plugs about two weeks ago, and its been running fine ever since with the exception of an unrelated spark knock that I've been trying to cure for a while. I believe the spark knock is from a mixture that is a bit lean that might also have aggravated the misfiring ignition by making it that much harder to light off the mixture, but the misfiring under load on rainy days has stopped.