Rewiring Car, Alternator Connection questions..

Basically you hook "all wires" together there at the ballast and things takes care of themselves.

If you have an original 4 terminal ballast, one of the wires also goes to 12V and the other goes to the ECU. Both these can be eliminated.

The old coil POS wire now goes to your MSD "small red." The big red and big black go to ground, and to the starter relay "constant" 12V. I would fuse that wire.

The "truth" is that functionally you could leave the ballast alone, and hook the old coil + wire to the MSD "small red" and it would work fine. The small red is a low current "trigger" wire just like a relay

By the way MAKE CERTAIN you do NOT have anything hooked to the coil, NOTHING except the two new MSD wires. No tach, and no radio condenser / capacitor.