Here's some links to get you started.
Ammeter vs Voltmeter
Ammeter or voltmeter?
Ammeter - To bypass or not to bypass...
Insight into the 'theory' behind it all
Ammeter Bypass - what's this guy saying? (referring to the thread above)
$15 Ammeter/Voltmeter Retrofit write-up (missing pics, but has the part number)
More ammeter questions
Ammeter and alternator circuit breaker writeup
Engine Bay ammeter bypass w/ Pics
Quick and dirty ammeter bypass (not recommended)
Ammeter be gone-wiring question?
Ammeter vs Voltmeter
Ammeter or voltmeter?
Ammeter - To bypass or not to bypass...
Insight into the 'theory' behind it all
Ammeter Bypass - what's this guy saying? (referring to the thread above)
$15 Ammeter/Voltmeter Retrofit write-up (missing pics, but has the part number)
More ammeter questions
Ammeter and alternator circuit breaker writeup
Engine Bay ammeter bypass w/ Pics
Quick and dirty ammeter bypass (not recommended)
Ammeter be gone-wiring question?