That's also what I thought, but I really can't seem to get any of the pieces to fit into the adapter I bought. I definitely have the right one but I can't figure out how they're supposed to fit together in any configuration.You want to install an aftermarket head unit, right? If it's anything like mine, factory radio is a little 4" x 4" square thing, I'm pretty sure any aftermarket head unit needs to be installed in the center console where your factory tape deck/CD player is (directly in front of the shifter). You'll need a Sunbird-specific plastic mounting kit, and wiring harness adapter, from a company like Scosche. You'd then splice all the wires from that wire harness adapter to the corresponding wires on your aftermarket head unit's harness. Then just plug it in.
I assume you'll actually have to pull out the factory radio temporarily, just to unplug the wiring harness from the back, and snake it down to your new head unit in the center console.
I haven't actually done this on mine, but I might be looking to. And I saw a video of a sunbird that had a an aftermarket head unit installed in the center console where the tape deck usually goes. I "think" that's how you'd have to do it.