I have to wonder if these can really supply 200 amps and for how long. I
have used high amp windings and such on US cars. While they usually do
produce more current at speed, idle speed operation is often a problem.

The price of this alternator is not unreasonable if it performs as
expected. I wonder if it is new are an upgraded rebuild.

The stock Vanagon alternator does an excellent job keeping up with most
loads and battery charging. What is lacking is the power delivery. The
wiring is undersized, and after many years it is corroded further reducing
current capacity. Every switch and connection makes things worse. Unless
and alternator is needed anyway, I would look at wiring upgrades first
Then you will have the first part in place for a larger alternator.

Dennis