Had "issues" with the Autometer gauges in the 55. Called them, was told 2ohms or less on the connections to ground.
The 55 install is new, I'm anal about this stuff, still ended up with 20+ ohms on the ground side at the tank. [Grounded to the
welded in studs on the body.] Ran a dedicated ground from the tank hanger, directly to the batt.Now reads <.2ohm.
Same with the volt meter in the dash. Batt neg is cabled directly from the batt to the ft of the car, to the frame, engine and body. All with 3/8 bolts, star washers, yadda, yadda. Gauges were grounded the same way> welded 1/4" studs. 25ohms at the stud to batt neg cable. Cleaned, added No NOX grease,...WALA <.2ohms.
These same issues have arisen on the GN..Added grounds, checked and rechecked, cleaned. Gauges are much more accurate....
The Autometer tech made a comment I'd not thot of: The gauges are actually just volt meters, with different faces on them...
Back under my rock...