Replace the voltage limiter. I strongly suggest getting an electronic replacement and be done with it.
RTE sells electronic limiters on Ebay.
Also MR.Heaterbox builds and sells electronic limiters..

Just to be absolute sure...with a test light and the key on ACC or RUN,pull the wire from the sending unit,ground your test light and poke the plug for the sending unit. It should be dim and pulse on/off. If that does not happen the limitier is fried.
You can test the wire for the oil pressure and temperature gauges same way but with the key on run only.
Hope this helps,good luck.