I had the rallye gauges redone by a previous sponsor here and now that they are in the car they aren't reading correctly. The fuel gauge doesn't go to full (has new NOS sender) temp reads too high (have infrared thermometer) oil pressure shows 35-40 psi (used 3 different sending units). I'm at my wits end and if they hadn't been done 3 years ago I would send them back. Open to any and all ideas. Signed, VERY frustrated.

There are many variables that can cause the conditions you describe.
voltage to the cluster, voltage limiter, Bad grounds at the cluster or sending units, bad wiring / connections, bad sending units, bad gauge / calibration.

The quickest way to diagnose in this scenario would be to use a gauge checker which can be easily duplicated with 3 resistors 10 , 30, and 78 ohms and a 3 position switch.
Another option is to disconnect the appropriate sending unit, and use the resistors one at time. One end of the resistor attaches to the sending unit wire and the other end of the resistor attaches to a good ground. turn the ignition on and wait for 2-3 minutes or so for the gauge to stabilize. NOTE: Every time the value is changed the gauge requires the 2-3 minute window.

The 10 ohm resistor should give a Low gauge reading

the 30 ohm resistor should give a mid point reading

The 78 ohm should give a High reading.

This will confirm whether the sending unit or something else it at fault.

Report back and I / we will walk you through the troubleshooting steps.