A model # of the Hitachi alternator would help to verify exactly what you have but I believe it will work. Post the model # so I can look it up...
First thing you have to know: Your old alternator had a regulator. The new one does not require it, so some wiring changes have to be made. The new alternator requires the following connections:
1. A switched +12V wire commonly know as the exciter wire.
2. A charge wire to the alternator B+ terminal
3. Ground
The 10ga White/Blue wire with the ring terminal from your old alternator hookup connects to the B+ terminal on the new alternator. This is the charge wire.
The alternator will ground itself through the mounting bracket.
That leaves the switched +12V exciter wire. Here is how to get that easily.
First you need to order the following parts from me: Part# 3P8862W and Part #Jumper1.
The first part# is the connector that will plug into the back of the alternator. It has two wires in it. A BY wire which will splice into the new +12V exciter wire (read below) and a yellow wire that can be used to hookup a charge lamp if you want it.
The second part is a connector with a simple jumper that will plug into your old three pin regulator connector coming out of the harness and will use the +12V wire there and jumper it to the White Green wire that already goes from the regulator area to the alternator. This Green/White wire will be your new +12V exciter wire.
Once you install that jumper plug, you will cut the black three pin connector off the old alternator plug and splice the White/Green wire to the Black/Yellow wire on the new alternator connector. The White/Black wire from the old alternator harness will not be used and can be taped off.
If your regulator has a different connector other than a three pin, I would need to see a pic of it to get you the proper jumper connector.