Thought this was an interesting video.
https://www.youtube.com/watch?v=0qVfKiujK5A&feature=share
easier and better to just go this route https://www.rt-eng.com/index.php/RTE_limiter.html
Vans Auto also sells one. Their version has no terminal for the capacitor/condenser. I metered one of theirs and it's a consistent (non-pulsing) 5 volts.
https://vansauto.com/product/voltage-limiter-solid-state-ivr3/
In my 66 Charger, i modified its internal voltage regulator using a UBEC 3a 5v switchable 6v voltage regulator. When i bought it on Ebay back in 2018 they were going for as low as $3.97 so i bought two of them. On my Charger i found that the 6V setting gave more accurate gauges than the 5V. (Note: the original mechanical pulsing isnt really 5V put pulsing 14V when engine running and half of 14 is closer to 7 not 5. ) You do not use the condenser with it either. Works great it even has a small LED light on it to show its being powered and it is inexpensive. Right now on EBAY their going for $6.97 with free shipping. Just search for UBEC 5v/6v.
PS...i wired it in with long leads to the back of the ash tray area in the dash...so that...IF it were to fail i could replace it easily, AND if it failed HOT..i.e not reducing the voltage i could disconnect it quickly to save my gauges from burning out.