Mark,
If you read the excellent document on the Coolcat web site that Mike Eck provided a link to earlier (note it has multiple pages), you will find a detailed description of all components of the charging circuit, together with a troubleshooting procedure for each of them. Using these procedures will allow you to identify which component is faulty. You can then make an informed decision about whether to repair the current system, or replace it with a new one. If you do choose to replace the current system please remember that the wiring looms are sized for the current capacity of the alternator. If you "uprate" to 110 amps you must upgrade some of the loom or you may have an underbonnet fire in your future....
Good luck.
-David