I can't help you with the problem that you are having with your original style, mechanical voltage regulator.
However, I do have an upgrade suggestion that I think would be "money in the bank". There are replacement "solid state" regulators that are physically the same size and footprint of the original. The only difference is that the cover doesn't say "Delco-Remy" like the original one does.
Most starter/alternator/auto electric repair shops carry (or can order) this solid state replacement regulator. As I recall, price is in the $25-$40 range.
Going to the local Chevy dealership won't help. Although you can still get a GM replacement voltage regulator, it is the mechanical (original style). GM doesn't offer a solid state alternative. Although I am very much into "originality" when it comes to maintaining and restoring our classic Camaro rides, this is one area where you can perform an upgrade that definitely makes sense and it will be transparent (with one very small exception) to anyone who is looking.
If you decide to use one of these solid state voltage regulators, in order to keep the appearance "original" you will have to replace the cover with an original Delco-Remy cover from an original regulator. (The original cover has the words "Delco-Remy" stamped in it.)
The cover on the solid state regulators that I have seen are all held on by screws. The cover on orginal regulators was riveted in place. No big deal, drill out the rivets and the cover comes off. Install the Delco-Remy cover on the solid state regulator base, bolt it in place, hook up the connector and you are done - no adjustments - nothing to adjust. The one small difference in appearance is that the Delco-Remy cover will be bolted in place instead of riveted. To me a small concession for this reliability upgrade.
Both my 69 RS and my 66 Chevelle have solid state voltage regulators with original Delco-Remy covers and I haven't had any problems. 5+ years on the Chevelle, 1 year on the RS.