84-87 have a different taper on the shaft than 88. They are not interchangeable.

The line labeled 93-95 Camaro also applies to 88 Fiero as Raydar said. I'm not sure about 96-up Camaro, as the catalog I got this from stopped at 95. The Camaro and 88 Fiero parts are cheaper because they make more of those than the 84-87 parts.
Also note that it lists the thread as male on the Fiero part. That, of course, is incorrect.
Sorry about the picture size

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1986 SE Aero coupe.
3.4 DOHC swap is complete and running, now just have to finish the rest of the car...
[This message has been edited by tesmith66 (edited 05-07-2016).]