The alternator you have
does require an external voltage regulator.
The B+ terminal connects to the fuse panel, and the D-, DF and D+ wires connect to the voltage regulator.
If you want to use the older style mechanical voltage regulator, you would wire it as shown in the 1973 beetle wiring diagram.
If you want to use a newer style solid-state regulator, you would wire it as shown in the 1974 beetle wiring diagram.
(Check
www.vintagebus.com for the diagrams)
If you want to opt for a new alternator with integral voltage regulator, wire it as shown on our tech page.
Charge indicator light wiring varies depending on they type of voltage regulator used. See the diagrams for details.
Mechanical voltage regulators start at about $34.95 and solid-state ones are about $97.95. A new 51 amp alternator with integral regulator is $219.95 for the complete kit. Give us a call; we can get you anything you need.