Don't be surprised if you have a bad connection at either the bulkhead connector or the connector on the steering column. Look at the heavy red wire at both connections. Look for discoloration of the plastic. Pull them apart if possible and check them. I had the same problem on my 71 Challenger and I changed everything out. Regulators, alternators, had it to two different shops, nothing. I was under the dash one day just looking around and saw a brown streak in the connection for the steering column to the main harness. I bypassed the connector and that took care of the overcharging problem. Remember, these connectors are 45 alomost 50 yrs. old.