The strange clip on one of the studs is electrical contact, and heat shield, and heat sink. That stud gets pretty warm. So this hole in the board is larger and square. You'll find the housing is cut away a bit larger underneath too. All to vent some heat. By 67 year model they determined warm isn't too hot, so the same pal nut was used on this stud though same round hole, with a backlite cap covering it.
If you'll lift the gauge you'll find a slither of metal on its backside. This grounds the instrument regulator to the inst' housing. Sometimes a lost contact here is the only issue/cause of non working limiter. if you'll install outboard regulator anyway... Cover this slither of metal with electric tape. Now the backfeed condition mentioned in the ill-informed article you referenced cannot happen. Where the switched 12 volt wire serves nothing more than the limiter in your panel, you can take this switched 12 volt wire from harness connector and route it directly to your outboard regulator. Both steps render the original limiter totally isolated. It can't do anything ( dead in a coffin ). If you already opened your fuel gauge to disable the original limiter due to some other web page, you didn't truly need to do that.
Since the heat is no longer an issue, A similar pal nut or common 10-32 hex nut with washer, like those on your amp gauge, will replace that strange clip too.