To wire your factory ammeter and not use the factory harness for factory guages here's what you can do. There are two terminals on the back of the factory guage. Run one length of wire to the BAT terminal of your horn relay from one of the terminals on the back of the guage. The second wire is run to the junction block behind the battery near the radiator. As I understand it the guage measures resistance over the length of wire and gives you your reading. I would install an inline fuse in the wires to be safe. I am redoing the wiring on my 67 and am going to use this meathod of getting my now inoperative ammeter to work. Let me know how you make out. These instructions are on this site somewhere. I got them awhile ago but lost the e-mail. Good luck.