68 Barracuda........ Temp and Gas Gauge Issue.

One might think some of these members own stock in RTE. WHAT BRAND NAME solid state limiter DOES NOT MATTER ! Even the homemade add on like your previous owners attempt can provide 5 volts for these gauges just fine,, if done correctly. There are legitimate reasons to open these very old thermal gauges. "bend the little thingy" is not one of them. Disabling the original limiter is as simple as removing that previously mentioned little thin piece of metal from the back of the gauge.
So why would anyone suggest opening this gauge ? To see if it's cooked,,, and it very likely is.
The seeing and knowing leads to sending the gauge out for repair. Odds are you will send it to whoever you purchased a solid state regulator from. There, 10 years of smoke and mirrors were blown away this Memorial Day.