I suggest you get rid of the onboard PRV and get a good quality brand name (Watts, Mueller, Ford) PRV that you can install at the supply source. In my 40 odd years of installing municipal water systems, the highest line pressure I have seen was 180 PSI. A quality PRV should be good for at least 200 PSI, so if your system is less than that, one regulator will work for you, or you can get a two stage PRV that will do the trick for higher pressures. The manufacturer should be able to provide the max pressure that the PRV is designed for.
Whatever you choose to get, I would check the pressure setting at the RV the end of your supply hose before hooking it up to your RV. So...... put the new PRV at your source point, then put your hose on, and then put a pressure gauge at the end of your hose before you hook up. (there are some PRVs available with an integral gauge) Set it up with a valve so you can have a trickle of flow through the gauge because you will need it to adjust the PRV. To get to your target pressure, turn the nut/screw clockwise for more pressure, counterclockwise for less pressure. To fine tune if you want to, shut the valve at the RV end, and check the pressure. It will probably be a bit more than you saw on the gauge while you had a trickle of flow. I am comfortable with 60 PSI in my rig, but I definitely would not go over 80 PSI. Old plumbing and high pressure don't go together.
If you are happy, close the source valve, hook up to your RV, load it, and Bob's yur Uncle.
Hope this helps.
