Did a little more searching. Looks like the 84 also fit a bunch of Chevy and GMC vehicles, particularly the full size vans. The 85 and up seem to be Fiero specific according to the Oreilly compatibility charts.
Edit: By the way, the 85 up Murray part number is 70-3660. No local stores show in stock near me, but it does say "usually available in 24 hours", or "online". We all know that could mean anything.
[This message has been edited by Lambo nut (edited 08-17-2015).]