All Gauges Reading Too High?

[billdozer]

So, my Blazer has a weird issue that I'm hoping someone can help me solve. I tried searching but didn't find any relevant threads.

Truck is a '79 Blazer I picked up a couple months ago. The gauges (except amp meter) peg too far to the right/clockwise. Of course, I wondered if it was the senders or some other unrelated thing, but I changed the temp sender and the previous owner changed the gas gauge sender in the tank before I bought it and neither had an effect.

The temp runs past the center of the gauge but engine is operating at normal temp. Gas gauge shows way past full when tank is full and is actually empty around the halfway mark. Oil pressure shows way more pressure than usual, probably 75lbs.

So this got me thinking this stuff could be related? Is there a single resistor or some other device that everything runs through that could cause this or should I treat each gauge like as an individual issue?

The truck is very original and doesn't have any added on electrical stuff, janky wiring, etc.

Any ideas? Thanks in advance!