190e 1987 Guage Cluster Not Working

[classics]

The Instrument Panel Is Out Of The Dash, I Need To Know Where To Run A Ground Wire To And From On The Back Of The Clusterto Get The Guages Working Again, The Tach Side Has A Metal Plate/back, The Guage Side Does Not, It Is Plastic Only,therefore I Need To Know Where To Ground This From On The Metal Side And Where To Attach It To On The Guage Side,again , None Of The Guage Clusters Are Working, Gas,oil,temp,please Reply Asap ,it Is My Daily Driver,thanks.IT IS NOT A FUSE OR SENDING UNIT ALL CHECKED.