I bought a couple AC Delco O2 sensors on eBay, and he sent me one AFS75, and one AFS105. They look identical, except for the engraved number.

Now as I have reaserched a bit, aftermarket sensors say they are both the same, but on Shoebox's page, and a lot of other places, there is a difference. AFS105 is a little more expensive.

Are they really interchangable?

 

Is there something on my site that mentions the AFS105?

According to AC-Delco the AFS105 was used in truck/SUV engines exclusively. I don't know if they interchange, but I would use the same part number on both sides.
Not sure why the person sent you two different sensors if the auction did not state this.

 

I just saw the AFS75, and not the 105, so I figured they were a little different. I'll send that one back. Thanks for the help!