How to bench test my electrical wiring - Request

All of our oil and temp gauges, and majority of fuel gauges will read 20 ohms across the winding ( ohm meter post to post ). Some fuel gauges ( varies with model ) will read 13.5 ohms. This test proves the winding inside is good. It doesn't prove the bi metal beam is good and the instrument is accurate, just alive. If you go to the extent of powering and testing instrument response per those suggestions above, what will you do if/when you find it inaccurate?
Attempt to recalibrate? If its out of calibration there is a fault ( bi metal beam is cooked ) that cannot be corrected with re-adjustment. A few owners/members here have poked their screw driver into those little setup provisions on the backside and totally lost the setup.
Buy another used one? You're gambling here. Odds are a used of same age will be in similar or possibly worse condition.
Plan A for the novice... Just check continuity with a ohm meter. If its alive put it back and hope for the best.
Plan B, send them to a instrument service vendor. Is plan B the best plan? They are 40+ years old.