I am in the process of getting parts to convert my automatic to a manual. The flywheel is about the only thing I still need to get. However, it seems like everywhere I look (rockauto, o'reillys, fidanza, etc.) lists the same flywheel part number for 86-88. I know that the 88's have neutrally balanced flywheels and the previous years had balanced flywheels. So my question is why does everyone list the same flywheel for those years? And how could one be certain that they are getting the right part when ordering?

I just looked up what you were talking about using O'Reilly's website because they have an interchange. They have the flywheel listed to fit post '88 cars such as the Beretta and Grand Prix. These models never came with counterbalanced flywheels, so I'm going to guess it's the neutral wheel that's been mislabeled to include the '86 and '87 Fiero. The only way to be sure would to call the warehouse that is holding the flywheel and have them inspect the rear of the flywheel for a counter mass ( very obvious). Or order it and return it if it's wrong.

Good luck in finding the 87 flywheel. The shop replaced mine with a new one that was for an 88 as the vendor had only one fly wheel listed. The shop had my original flywheel resurfaced as they could not find any balanced flywheels. The shop wasn't happy to pull the transmission back out for the reinstallation.