Wiring upgrades and ammeter operation
The starter relay stud is BATT+, so running from ALT out to BATT+ bypasses the ammeter. There is a way to have your ammeter still work. You add a series diode pair to the new 6 awg wire. That will let all current flow thru the ammeter until the diode breaks down in forward-mode (~0.75 V drop), which is ~3/4 scale on your ammeter. The excess current will then shunt directly to the battery (thru 6 awg wire). Don't buy 1/4 W diodes at Radio Shack or they will vaporize in 0.1 sec. Read my thread for the PN of a 200A diode, and heat sink it. Don't attempt if you don't know exactly what V = i*R and P = i*V means and how to use, and ignore the posts by a guy trying to argue basic electricity with an engineer.