Sure is a pretty alternator!
You do have the correct regulator. You can drill the tubular rivets out and replace them with screws if
you want. That will enable you to observe the visual condition of the innards.
As Shannon says, the manual may give you some help. Here are a couple things I learned in MANY years of
using them:
1. If the alternator charges OK but the amp light stays on with engine off, the fault is in the isolation
diode(s), the round thing pressed into the center of the red plate. Later models have two of them.
They can be replaced but they have to be NEGATIVE polarity because of the way they are mounted (backward).
They are pretty easy to knock out and replace. I have had a number of them go bad.
You do have to solder the wire onto the lead. Be SURE your insulating washers are OK or replace them.

2. I also had a mysterious non-charge situation when everything tested OK on my 164.
I spent WEEKS with it and finally found out that although the belt was fairly tight, it wasn't tight enough!
Once I got it GOOD and tight it worked fine.

The hose goes to an electric heater for very cold nights? Where does the other end go (where it returns to the engine)?

--
George Downs, Bartlesville, Heart of the USA!