I run electric aftermarket oi lpressure gauges since i hate to think about a mechanical oil pressure gaguge springing a leak in my interior while cruising on the highway. Aftermarket electric oil pressure gauge rspond immediately to changes in oil pressure. Stock factory gauges are very slow to respond. I have never found a correlation betwen the lines on the Dodge oil pressure gauge and any specific PSI reading.
I have used cheap $20 electric oil pressure gauges that worked fine but in my 89 Ford van I run autometer ultralite gauges. I get them used on eBay when I can find a good deal on them. Large auto parts stores should stock cheap electric gauges.