Actually, those red wires are supposed to be brown. Comes from the "Bat" terminal on the regulator to the strip just below the 20A fuseholder. That strip is just a connector. From the other end of that connector strip, another brown wire goes forward to the "Gen" side of the ammeter. From the "Bat side of the ammeter, a green wire goes back to the junction box and connects to the big terminal on the starter solenoid—the one that the battery + cable is on. So, following the electrical flow, the regulator output goes to the ammeter for measurement, then color changes to green going back to meet the + battery cable at the solenoid. If you balk at using an ammeter, you can just eliminate the wires going forward and back and instead just connect the brown to the + cable side of the solenoid. But you still need the green wire to feed the ignition switch (or choke/start buttons)
The 20A fuseholder is common with the connector strip just below it, and serves to fuse the auxillary power take-off on the bottom of the junction box cover.
