rewire the alternator

So I want to get some or all of the amperage not going through the ammeter, I figured I would wire in a voltmeter, now I did some research on these forums and of course now I am confused, hopefully someone will help, I have gone and looked at the MAD circuit rewire page and it says its for a dodge truck is that the correct one?? Catalog

after looking at that I cant eliminate the wire from the alternator going through the firewall, and just go with a fusible link directly to the starter relay stud, if I do that then I have no power inside of the car? So that is why I have to run some supply line into the car but not attach it to the ammmeter?? Ok let me rephrase this what should I do, if I keep it like it is and just add a wire with a fusible link, go directly to the starter relay and leave every thing the way it is would that make any difference?? I guess I am worried about putting 60 amps or what ever the stock alternator puts out through 30+ year old wiring??