Bypassing the Amp gauge - Question about the MAD Electrical method

Xtreamist said
The car did run, needed some minor work but it started and ran the way he had it. Has a Mallory dist. too

View attachment 1715268136

This is as much as I can figure so far.
The biggest question is how does the alternator output connect to the ignition and battery?

Switches
1. Tach. But maybe also something else?
2. Start. Apparently powers starter relay?? In which case, S2 yellow has to ground somewhere.
3. Run. Power to ignition coil and MSD 5900
4. Gage Illumination.