volt gauge or not?

Ok, well I just read through the tech section in the search venue above for by-passing the amp gauge, ( very well done article by the way ) well it looks like I have two vehicle's at our house that need and will be getting this wiring upgrade soon, the 74 Duster and the 80 Dodge truck, but what it didn't say in the article was if anyone has put a voltage gauge back in the car, and if so was that getting wired with its own dedicated wires through the firewall somewhere? what are you guys doing after by-passing your ammeter?