Stealthy Electronic Voltage Regulator tip.
For those of you restorers out there who must have an original NOS stamped Delco external regulator for appearance and judging reasons, but hate the constant trouble with that prehistoric mechanical regulator, there's an easy and stealthy fix that won't cost you points at the show.
The trick is simple. Keep your stock NOS Delco regulator box, but open it up and install an electronic voltage regulator inside. What kind of regulator? Easy! You can easily wire an LM317 voltage regulator into the inside of your old mechanical regulator box. The LM317 is a cheap, easily available 1 amp regulator chip, and is widely used by electronic tinkerers everywhere. You can buy one at Radio Shack for about 3 bucks. There's even a schematic on the package.
The mechanical voltage regulator is a complex device doing a simple job. There is no voodoo going on in there. Back in the days of the dinosaurs, the sole purpose of the mechanical regulator was to act as a hi-lo switch to alternately load and unload the alternator with a roughly calibrated reference voltage range. This was so that your alternator could get a rough idea of system voltage and thereby (in theory) not overcharge the battery. Your alternator sees the reference voltage as a measure of battery condition and charges or idles accordingly. In contrast to your mechanical vibrator masquerading as a regulator, using the LM317 the output is held at precisely the voltage you select. Your battery is very happy, your charging system is stable, and no more "stuck regulator syndrome".
Don't let the term "chip" scare you, either. The LM 317 is a three lead package. The circuit is SIMPLE! Follow the schematic on the Radio Shack package, or look online. Physically, you can simply disconnect your mechanical regulator wiring inside the box and substitute the LM317 on the appropriate leads. It is quite small. Hide the whole circuit inside the old regulator box. You can even mount a trim pot and trim the output of the LM317 to precisely the reference voltage recommended in your GM service manual.
When you connect the regulated output of the LM317 to the factory wiring which feeds to your stock old school GM alternator it will keep your charging system at that same reference voltage at all times...just like a modern electronic regulator. Steathy, cheap, and WAY better than the old mechanical regulators!
Now you can have it both ways... original wiring, NOS regulator box, happy judges and the comfort and ease of an electronically regulated alternator.
An added benefit is that when your system is at nominal charge, the regulator won't be cycling off and on and off and on and off and on...causing your lights to get dim and bright dim and bright dim and bright... AHHHH!!!!