Just put the Solo's on a friend's L99 yesterday and can confirm that the O2 sensors are different.
Solo emphasizes to keep them in their original positions.
If you're going to ignore Solo's instruction to not put the sensors in until the cat's are in place, (like I did) be aware you need to put the mounting bolt and flat washer in the adjacent hole before scewing in the top sensor (it blocks the bolt hole once in place).
This is actually a good thing as it holds the bolt in place while you put a flat washer, lock washer, and nut on top of it (and get it started) while lying under the car- by feel, holding the HFC in place with the other hand, if you're doing the install yourself like me. It can be done!
But it may be a good idea to have a little help around.
