Yes, the oil extension was required due to the revised brackets for Firebird models, the regular angled brass block in the top fouls them. Don't lose the extension tube, the reproductions are rubbish and too long. This means the sender gets pushed past the loop bracket retainer. They don't care too much because the sender they sell is too large anyway so you can't use the bracket and then won't know it never fit. I did a post on here once years ago about comparing and modifying to fit. These parts still don't exist in reproduction, just the incorrect tube, so make that all 3.
Edit. No, looks like thread long gone. It was about 12 years ago as I had to drive the engine shop to test fit for pics. But it had been referenced numerous times, seemingly still pre-crash. I'd post it again but not sure anyone had any real interest then or now!
Edit 2. I found some of my posts in another forum that blocked me, that's what you get for being a major contributor. Seems also that there may now be a repro bracket and small sender in the works, I need to study that one further.