The alternator harness will be different from the stock to the HD alternator. If you don't want to go throgh the hassle of trying to find the correct harness (if you don't have the one from the donor car), try upgrading the alternator you already have. There are kits available from JCWhitney that will upgrade your 45-65 amp alt to 100amp or some higher output. They are a bolt in swap, and relatively easy to do.
Nine times out of ten, installing one of these kits will cure a 'bad' alternator since you will be replacing just about everything inside the alternator. It has been quite a few years ago since I did my last one, but I think that the kit comes with the stator (outside windings), a heavy-duty diode bridge (that's the part that makes the output DC) and a new set of brushes.
For the purists out there, there will be no outward change to your alternator, so you can even keep the original date coded case from your old one. A nice cosmetic touch would be to have the case glass beaded to bring out the original color and shine. You will be reusing your old pulley and fan so again that's a plus.
Yes, the voltage regular can be removed along with the harness, as the one-wire has an internal regulator. You may or may not need to run a wire from the S terminal on the one wire alt to the starter solenoid depending on the year. All in all, it cleans up the wiring tremendously.
Mine is a Chrome 140amp one-wire Powermaster alternator. Cost me $239 from summitracing.com. The Non-chrome, black thermalcoat one is $189, and I think the 100amp one wire black thermal is $159.00... If you really wanna go nuts, they have a 200amp version, but that's a bit much.
Not cheap, but really nice piece of equipment. I also picked up a set of $20 chrome alternator brackets while I was at it. Looks good with my Polished Victor Jr waterpump.
Only word of warning is to make sure you understand the instructions when installing and also that it ships with the serpentine pulley installed, but DOES include the V-belt pulley, if you have an impact, it's no problem to swap...
why would you have to run a wire from the "S" terminal on the powermaster alternator to the starter solenoid? I have a standard, 67, would I have to do this and where on the starter solenoid would I have to hook it up?
Running a wire to the solenoid allows the alternator to "sense" how much power to output. The battery side of the solenoid acts as a junction block where all of your electrical accessories join up. This is where all of the draw is so it's a good place to let the alternator how hard it has to work. This is not necessary on a one-wire though.