Originally Posted by Custom88
I changed my 88'* a little while ago.. The tip of it was just slightly smaller than the threads of it. The stock one was smaller though than the new one (old one was AC Delco, new one is Bosch.. bad choice from what I've heard.
Well, maybe so, but to answer the original question: Depending on which AC-Delco O2 sensor you put in, its body may or may not match the old one. For my '93 SEEi, there were no fewer than three different AC-Delco part numbers listed as acceptable for it. One was a retail replacement part number that came in a box, the other two were dealer part numbers, and the one of those that was in stock came in a plastic bag. The boxed unit had a wide-body metal shell on it; the bagged unit (which I eventually bought, since it was $3 cheaper) had a narrower one, sort of like a spark plug.
I passed my emissions test the next day.