Nope. The AC ones are totally different. For whatever reason. Not sure why, but they are. Where did you see 5 different ones. They vary over the years, again, for reasons unbeknownst to me, but there is only 1 for you. Those parts stores usally just lump them all together. That's why I hate parts stores. Classicindustires and LMC truck list what you want. Both $16.95. And both those places *usally* send real gm parts anyway for this kind of stuff.
Or, I can't read the full part number on that thing in your picture, by if you can, try typing into gmpartsdirect.com. My GM parts book for 1979 lists 9796480 as the correct number, but it's been superceded, and I don't know by what, but any dealer could tell you.