Well, I screwed up. Laugh at me. I had the Ranger apart to change the passenger-side O2 upstream sensor because of a code, could not break it loose from the bung despite using Freeze-It penetrating oil, and managed to round off the hex with the sensor socket. The angle wasn't ideal for tool access because of everything around it, even though I had the fender liner out.
Will take it to a muffler shop. I'm guessing dropping that cat will be necessary to remove that sensor, and I might as well have that downstream sensor changed as well once the cat is out.