The Chilton's manuals I have do not go into good detail about all the existing Bugs wiring.  For example, the key switch specifics are pretty lacking / incorrect -- one page lists the "Start" wire as Blk, and another lists it as Yel/Blk.  That seems incorrect.  Also, no mention of the "On" wire color.  And no mention of the 50 other wires exiting the steering column!  So on to other resources....

Found a mention of another brand of service manual (Bently, found this one), but before buying with fingers crossed, going to look at alternatives.  

Edit:

Jackpot!!!  At first glance, looks like this will clear up everything!  Clear wiring, detailed symbols, test points, and a detailed key that even includes fuse descriptions!  This is awesome (assuming it's correct for my 73 super..fingers crossed)!!  Found from here: https://www.thesamba.com/vw/archives/info/wiringt1.php

Before my edit above:

Found this from Jbugs.com for a 72:

Key switch Operation:

And some notes from a post here: https://www.thesamba.com/vw/forum/viewtopic.php?t=633701

• Looks like Red 4.0 mm is incoming power
• With the ignition switch in the ON position, two wires will be shorted and allow current flow. Likely the red (#30) and the black (#15) wire.
• The black/red (#50) wire should not be connected to anything in this position.
• Turn the key and hold it in the START position, all three wires should be connected together (red, black, black/red). This is how the red wire powers BOTH the ignition (#15) and the starter solenoid (#50).
• The grey wire is optional and may be either grounded or powered while the ignition is OFF with key IN. This would set off a door buzz

Going to put a battery in her this weekend, bust out the meter, and do some testing to at least figure out the key switch and how I'll integrate it with the Zilla controller.