My suspects.........
1. Your hacked up wiring is not connected correctly or wrong gauge.
2. Bad regulator
3. Mismatch between reg and alt
4. Alt. is higher output than wiring can handle (were those fusible links really only 30 amp??) Seems to me that if the alt is putting out full amperage to charge the battery, the whole current flows through the ammeter and the fusible link to get to the battery. 60-70 amp output....30 amp fuse....sounds like the fuse is doing it's job!
Thanks, Mark