Don't replace the regulator until you actually MEASURE the ground and hot side drop, it's easy:
With engine NOT running, and key in "run" stick one probe on the battery pos, the other on the regulator IGN terminal. You should not see much, not more than .2V (two tenths). The more you have the more it indicates a harness drop problem, and the more you have the more it will OVERcharge.
Now check the ground. With the engine running at an RPM to simulate "low to medium cruise" and the battery "normalized" stick one probe on the battery negative post, and the other directly onto the mounting pad of the regulator. Be sure to stab through any paint, etc.
Here again, you want a low reading, the lower the better. The combination (if any) of the two voltage drops---the ground side PLUS the drop in the harness ADD to the charging voltage set by the regulator
IF these two checks are OK, you either have a bad regulator, or in rare cases, a problem in the battery itself can cause this.
On my 67, before I rewired it, I had ONE VOLT drop through the bulkhead.