Fuel and oil gauges pegging

I would pull the dash at this point.

Get it on a bench and hook it up to a 12v source, car battery, 12V DC wall charger, etc.

Then do some checking.

The chassis of the cluster MUST be grounded to the negative of your supply.

Then you can check the IVR output on the back of the cluster. And do other propper testing of the guages.