Welcome from Austria.
Exactly. Powermaster makes CS130 as one wire alternators, they don't need the resistor.
Lot's of info in that thread.
https://www.gmsquarebody.com/threads/cs130-alt-wiring-on-85-c10.34899/
It's connected with a hose or pipe the valve cover, this is the inlet for the air that the pcv valve sucks out. You can put on a valve cover breather and use the opening in the air cleaner housing for your sensor.
Go to a car A/C shop, they should be able to repair the radiator. If fixing the leak is not possible Summit has direct fit copper/brass radiators and they ship to Europe...
It had screws in the ends. When I ordered them I got 2 left side weather strips so I cut them and glued them to the door. Returning parts from Europe to the US is expensive as I would have to pay the shipping.
This thread from 67-72chevytrucks has some good pictures...