Alternator & Belt
The 4.9 uses a 6 rib serpentine belt with an automatic tensioner. The tensioner is removed as part of the power steering pump, which is not only not needed, but also will not fit in the Fiero engine bay. There needs to be a new way to adjust the belt tension. Some have come up with ways to incorporate an automatic tensioner from another application. I think that's a good idea, but I haven't put much time into figuring it out for myself. For now I am satisfied with what I have.
The stock Cadillac alternator will fit under the Fiero hood. I have used them on both notchback and fastback cars. The Cadillac alternator seems like the best choice because it usually comes with the engine, and it has a high output rating. Below are a few pictures of how I've modified the Cadillac alternator bracket to provide belt tension adjustment.
The bottom of the bracket is cut out to allow the alternator room to pivot downward
The rear hole is also slotted following the arc of movement of the alternator.
An idler pulley is added to the front of the engine to take the place of the power steering pump pulley.