alternator wiring

no alternator will put out more voltage then what is called for regardless its capabilities.
While all the current inside the cabin does go through the ALT' gauge, that's all that goes through it.
If you intend to add equipment that will require a higher output alternator... fine. That equipment would be supplied through relays ( very similar to how your starter is wired ). The ALT' gauge and those wires are not effected.
There are causes for the meltdown shown at the Madelectic webpages and more practical reasons to change to a volt gauge.