alternator wiring connections

I am assuming the aftermarket (Bosh) alternator is a replacement unit not something you are trying to adapt. If it is then, ground one of the field terminals to the case of the alternator (doesn't matter which) and connect the other one to the green wire from the regulator. You have to have a circuit from the voltage regulator to ground through the field windings in order for current to flow and create a magnetic field before the alternator will output current. The regulator will switch the voltage on and off to regulate the output of the alternator.

Sounds like the alternator is one that could be used for 70 up systems where 12 volt is attached one field terminal and the other is grounded through the regualtor. But in your system you have to have one of those field terminal grounded.

Also, you should be reading close to battery voltage on the green wire from the regulator if the other field terminal is not grounded. I would check connections and the ground on the regulator to.

The output wire from the alternator goes through the firewall bulked connector to the amp gauge, back through the bulked connector to the battery. This is a commonplace to have bad connections or a bad amp gauge. Make sure these connections are clean and tight and you have continuity from end to end.