Erratic Gauges

So I will be heading to back to where the car is in the next week or so and I will try that ground issue, try that resistor tool (already made one with those resistances, thank you), and see if that voltage regulator change would do anything.

Just brain storming, but if there was a ground issue with the wiper switch or the voltage regulator needed to be changed why would those issues only affect the oil and temp gauges and not the fuel gauges? I am just trying to understand the problem...