Transistor in rally gauge ?

Nice to describe your car when asking such. Yes, early cars had the Vreg inside the dash fuel gage, which lasted until ~1973 in the Rallye gages. No transistor, it is a wire heating wrapped bi-metal leaf which opens and shuts to maintain 5 V (on average) for the fuel and temp gages. I replaced w/ a $30 electronic one mounted outside from ebay (search "voltage limiter" and Plymouth). Mine has a trim pot to tweak the voltage to help perfect your fuel level reading, and those give a steady output. Some sites have photos to show how to disable in-gage Vreg (I slid heat shrink over the leaf). BTW, the later shiny rectangular cans which clip on the dash board in ~1967+, are the same thermo-electric mechanism and can similarly be replaced.