Another follow up:
Yanked the alt back out and reworked the mounts to remove the remaining suck, moved alt toward flywheel a ~6 mm so the belt alignment was right.
(bracket I made was for the OG Vanagon alt, just mounted in the std T4 location/std belt, the GM alt was different offset)
The idiot light issue was really idiot related, alt AND idiot light works fine wired to "L" terminal.
(Never trust wiring diagrams, look at the part)
I get 14.3--14.5v at anything off idle, and 13.7 at 800RPM idle with everything I have turned on.
(I usually idle it at ~1K, turned down to test alt. It still kicks in at <500 crank RPM)
Still need to add a ~560ohm resistor across the idiot light in the gauge head as a blown-bulb fail safe, may just put LEDs in while I'm in there.
Also redesigned the tensioner bracket, it is on the backside of the alt now and very simple to make/adjust.
(pics will follow---insert here)
The way the setup is designed, I can drop/replace the alt simply by pulling the collector bolts, swinging the muffler down on its hanger, and removing 2 bolts, ez-in/out no issues access for my fat fingers, actually far easier than the factory T4 alt R&R.
As to the Vanagon shroud cooling effectiveness... #3 CHT dropped ~30-50F at cruise with NO other changes, and CHT actually drops some when ... matching speed with Dallas traffic for extended periods at well above a T1s design cruise speed
Unless I accidentally fixed something with the flaps (they looked fine, reused same flaps) that's significantly better.
...Temp compensated meter setup, cal checked recently, same TC/meter before and after, same OAT and drive/speed.
I currently only have a TC on #3, so I cannot comment on balance ATM, working that.
Lets just say I'm on the lookout for more Vanagon housings...
The only "complaint" I have with the alt is GM installs a single 12ga fusible link to this sucker according to the manual...
WTF how does that go with a 100+A alternator? (12Ga COPPER is good for ~20A, and a fusible link isn't as good a conductor)
I'll probably wire in a high amp fuse at some point, still running 3X12ga to the starter.