1971 Challenger with Rallye Cluster. Coming back from a show yesterday, I noticed my gas, temp and oil gauge acting erratically fluctuating from max reading to normal readings. Normally I would think to replace the voltage limiter but when the gauges were acting up, the tachometer would drop to zero momentarily. That's the head scratcher. Would a bad dash/gauge ground cause the voltage limiter to send 12 volts to the gauge? Gauges don't peg hard, just climb to max reading a drift from 3/4s to max, then drop to normal for 5 minutes before doing it all over again.

i have chased dash gauge problems, as well as engine running problems, that finally ended at the tach causing them.
check the tach wiring, especially the ground.
it could also be where you are picking up the 12v source. check that as well.

tachs usually have 4 wires.
12v source, ground [usually some place on the dash or gauge cluster], a signal wire to the coil [negative post], and a light wire [usually tied into the dash lights so it can be dimmed along with the dash lights to your liking].
chasing intermittent wiring issues can be very frustrating at times.
if you have any splices on the tach wires themselves, that is another place to look at.
you can fix this ! we can try to walk you through the trouble shooting process, and when the problem is fixed [even if you need to replace the tach] you will have learned something and will be proud to say you fixed it yourself.
it took me YEARS [and then some !] and my lifetime up to now, to be able to fix or repair almost anything on a vehicle, and even today, there are times these things pi$$ me off so much i want to take a torch to 'em !
hang in there !