Stock charging system can be adjusted to work fine. It must be several CB's using same regulator and similar rectifier .
CB550 or 750 use same system, right?
Here my CB750 experience.
Look into the CB500/550 manual to compare if the charging system differ.
CB750 shop manual chapter 8
http://forums.sohc4.net/index.php/topic,168972.msg1959161.html#msg1959161Important that the connectors on wires from-to alternator windings are cleaned, no corrosion. All 3 yellow, white, green where they are connected inside front sprocket cover.
Next connector the bigger white behind the carbs.
Clean the regulator connectors and relay connections. Point gap and core gap. Tighten the regulator connectors white, green and black with a plier before connecting them.
I have adjusted 3 different regulators on my 2 CB750.
Both bikes have a voltage display between tacho and speedo so I can see the charging while riding and how it will change after 1/2 hour ride. 1-2 hours.
Most important to have correct core gap. The manual say 0.6-1.0 mm
I have learned that it should be 0.8-0.85mm. Not more more nor less.
0.6-0.7mm will end up in too low voltage. Not reaching 13V.
0.7mm can cause sudden drops to low 13V while riding despite over 4000-4500 rpm.
0.9mm and more can suddenly cause a sudden voltage increase. I saw how it after a 40 minutes ride suddenly increased from around 14.5V to over 15V still climbing over 16V. I had to turn Hi, blinkers and brake light on to fight back while riding back home. I was worried about my Dyna-S ignition.
Regulator adjustment:
# Point gap 0.3-0.4 mm.
0.3mm feeler gauge goes in by ease. 0.4mm not.
# Core gap: 0.8mm by ease, 0.9mm not. Better closer to 0.8 than 0.9mm.
Adjust voltage screw so 14V is reached at 4000-4500 rpm.
I really recommend to have a voltmeter display to read while riding.
Check what it show compared with a voltmeter when measure direct on battery. From idle all the way to 5000rpm. It can differ 0.3V or so. Remember an eventual diff so that can be added.
If you cannot read voltage while riding, do not adjust to 14.5V . Voltage will increase when battery is charged to max again that happen after 1/2 -1 hour ride.
Using brake light, blinkers etc will decrease the voltage, it takes time to reach full again.
I have changed to LED rear light so brake will not affect as stock 21W.
Important with a fully charged battery when adjusting voltage and read max.
I'm fine with 14V as minimum at 4000-4500rpm. 14.7V or 14.8V for a short while.
I have used these voltmeters for several years and many hours looking at them during countless of km. Must be over 40.000km now.

Forum member Dave in Australia use a Bosch regulator for cars on his CB500.
Search the forum and find.