Sorry Dennis, but your insight does not help this fellow racer. I've run both Longacre Acutech Sportman and Longacre new stepper motor oil temp gauges and NEVER had a problem. An oil temp gauge can be a very useful tool if monitored and not just installed in a car for looks. I've worked in an air cooled 5-40 HP engine test lab for 32 years and I can tell you that anytime oil temps get above 300 deg F using a base or non-synthetic oil, it is not good and oil will get very dark in color and may smell burnt. If you're running a full synthetic oil then oil temps up to around 325 deg F are OK yet. Thus, you can see what your temp is after a race as a wat to determine next oil change. On dirt my oil temp with a 10W-40 synthetic oil has not gotten above 250 deg F for a 20 lap feature and thus I have been able to change oil only every 3-4 races. I do understand that on pavement the oil temps get hotter as the engine works that much harder for that application. If oil temp is exceeding above listed values and turning dark or black, it's time to change oil. Sure, you can observe oil color in viewing window, but it sure is nice to see how hot it is getting at the track and gauge also can give you a point to shut off your cooling fans after a race.
Just my opinion! Now back to helping out this fellow racer.
1934 sedan...Need more information. What brand? Electric or mechanical sending unit? I assume you have a good 12 vdc supply at gauge and supply wire to gauge is fused?