why wire an ammeter at all.
keep the real high amperage stuff OUT of the cab altogether. use relays were you can and a volt meter.
stock is stock but a safer way IS better.
my .02

it's your truck.
' Amperage is a measure of current flow, and
ALL of the current used to the vehicle as well as recharge the battery was routed through this
one gauge–which caused the gauge to display the battery charge rate. Both the alternator and the battery were mounted up front passenger side, oppisite, under the floor. And the AMP gauge was at the dash. It was an arrangement resulting with a very long wire circuit charging the battery.
http://www.madelectrical.com/electricaltech/amp-gauges.shtml