If you are trying to run a 100A alternator on a stock harness, YOU BETTER bypass the thing. First start by reading the MAD article:
Catalog
Now, you don't necessarily need to do so as they did here, but this article goes through the "why" of ammeter/ and bulkhead connector damage. You can buy new terminals, or you can drill them out and run larger wire through the connector body.
You can bypass the ammeter by running a direct FUSED wire from the battery direct to the alternator. FUSED
Then (with battery disconnected) unhook the ammeter and check the wire ends, and if they appear to be OK, bolt them together and TAPE them Then you'll need a voltmeter or other device to monitor the battery
