Since the OP was asking about swapping out for a chevy alternator, I did a Google Search:"Swap a Volvo Alternator for a Chevy" and this was the at the top of the list:
http://forums.turbobricks.com/showthread.php?t=1069
and this was second:
http://forums.turbobricks.com/showthread.php?t=1069
(Actually, this was linked on the first listing)
I did a quick peek at the second link, and if you have even a modicum of ability it should be easy. It explains what to interchange, and what to do when the GM alternator is laid in place to figure out the changes to the mounts. But if you have never torn down an alternator to change brushed or a voltage regulator then you have some studying to do. Don't jump into this blindly if you think an "Ohm" is a Buddhist meditation chant.
From what I see, You need to swap out the pulleys, and you will need the GM alternator bracket (I am assuming the is what is being called to "black arm thing" in the post). You will also need the appropriate connector to go with the chosen alternator. if you are getting the GM Alt from a salvage yard, grab the bracket, and just cut the wires leaving 8-12 inches with which to work out the splicing. The article talks about getting the terminal designations and picking up a wiring harness plug (see cut wires at salvage yard). The newer the alternator, the more complicated the harness plug.
You were asking about part numbers. Well there really are no exact part numbers. It hast to do with what looks close to your original alternator. One thing to research is if you have an alternator that is externally regulated. I do not have experience with early Volvos (or much with late Volvos for that matter) but I don't know if any of the systems had voltage regulator mounted off of the alternator. 1982 appears to have both internally regulated and externally regulated. But the external regulators were still mounted on the alternator. It only makes minor differences in your wiring changes. A good place to get visuals, and amperages (which will also give you part numbers) is Rock Auto. You look up the make, the model and the year, choose electrical and then alternators. all will show the rated output, and most will show photos. First try to match the appearance of the target alternator with the original alternator, it need to have a similar mounting pattern.
If your alternator looks like this:
Then DON"T get one that looks like this:
or this:
You will need one that looks like this:
or this:
This is not as complicated as it sounds, but it is not a easy as changing wheels. If 100 AMPs will be enough, then go for the Denso, it was available on a number of Volvos from the late 80's on. If you have a sound system that makes the headlights flicker when you crank up the volume, then you might need to look for 140 AMPs or more. I am not going to go into Volts/AMPs/Watts here, I might get banned for taking up too much server memory. It is all in the research.
