Temp and Fuel gauges trouble

The VR must be grounded. The condenser is only for radio noise. Input to VR is 12V to a ground point on the cluster (there's a common trace grounding all the illumination lamps, etc)

On my 67 there was "a whole bunch" of stuff wrong

Broken / loose connector pins, broken loose from the circuit traces

Loose / corroded nuts on the gauge connections.

On mine, the springy fingers that make the connection on the VR were not making contact with the board traces. I had to solder jumpers across to make contact

Also, it's a great idea ot connect a ground pigtail and bolt it to the dash frame