Magnum swap using Magnum alternator

You will still connect the rest of the car as usual. The old setup had the main charge wire going through the bulk head, through the ammeter, and then to everything in the car. When you make a new charge wire going from the alternator to the battery you are making sure all high amp charging goes through the new circuit that is large enough to handle it.

Next you bypass the ammeter using one of the methods you find out there on the interweb (this site). When you do this you are not just disconnecting it, you are bypassing the ammeter or doing a voltage gauge conversion, but you keep the the rest of the car powered up otherwise the same way.