There is a reason the guy at EZ Wire is selling parts instead of fixing trucks- - - -his ignorance is showing bigtime. Even if the original ammeter (not voltmeter) pegs momentarily after startup, it's not going to destroy the gauge or start any fires. Using an 80 amp alternator is a foolish exercise in overkill on charging capacity, but it's not that critical. Run a #8 wire from the back of the alternator to one side of the ammeter, and another #8 wire from the ammeter to the battery cable connector at the starter. Tap all the electrical loads like ignition switch, light switch, etc. off the side of the ammeter with the alternator wire on it. The ammeter will show "charge" and "discharge" normally, just like it did 50+ years ago.
If you're worried about the ammeter pegging out right after startup, cut off a piece of stainless steel radiator hose clamp about 3" long, bend it into a shape resembling the "ohms" symbol on a wiring diagram, and drill holes in the ends so it can attach between the terminals of the ammeter. This shunt will carry the majority of the charging current, and the gauge will deflect a little to indicate charge or discharge. Problem solved!
Jerry
