Instrument cluster voltage regulator, on a 1970 Plymouth Valiant, 340 Duster

Hello where is it located on a 1970 Plymouth Valiant, 340 Duster ?
It is not on the back side of my instrument panel.
Is it inside the panel or on the firewall, under the dash?
My temp & fuel gauge read zero...
I would like to check the IVR if I could locate it!
Any help or pics would help and be appreciated.
Thanks in advance