Kevin,
Assuming you are retaining the 6 volt positive earth system, refer to the original wiring diagram and wire the 4 terminals of the solid state rectifier as follows: + to earth, - to 6 on the switch (blue wire on original diagram), AC to alternator (brown wire), AC to 3 on the switch (red wire).
I think I saw in one of your previous postings that you are going over to 12 volt. If this is the case, other alterations to the wiring will be needed. Wire up the rectifier as before but omit the red wire. Join together the yellow and green wires from the alternator and connect them to the vacated AC terminal on the rectifier. This will now give you full output from the alternator irrespective of the switch position. You now need to wire a Zener diode between the negative terminal on the rectifier and earth (make sure you get the correct Zener diode (positive earth) - this will then control the charging voltage and prevent the battery from boiling dry. The Zener diode will need to be mounted on a heat sink as it can get very hot when dealing with the full current being generated by the alternator.
Regards,
Eddie.