For proven dependability you should consider original equipment for a stock engine, I arrived at that conclusion for pretty much any part that will stop a car dead in its tracks if it fails and is a difficult part to replace. If power upgrades call for more performance then look elsewhere.
Centerforce peformance clutches have a very poor performance history on the Fiero forum where most engines they were used on were modified calling for a stronger than stock clutch. They performed so poorly that no one their with any knowlege of their history in the Fiero will buy them.
Spec gets the most buisness on the Fiero forum but have had some trouble with hub failure particularly with V8 and 3800 applications as well as on several occasions sending the wrong combinations of parts as documented in forum threads and well talked about. There was a lot of speculation and blame placed on the old Fiero transmission being the cause however, no one explained to my satisfaction at least why the problem seemed to consistently occur with the Spec clutch. The remedy was swapping to a solid hub which I felt was to much of a compromise.
I personally took my stock 3900 clutch which is much stronger than any of the previous 60 degree clutches with a measured ~ 2000 lbs clamping force, to a local builder and had it converted to kevlar friction material. I also had the option of having the spring pressure in the pressure plate increased but the builder suggested I leave it as is considering it already had more surface area and about 400-500 lbs more clamping pressure than the stock Fiero clutch.
This is the second clutch I've had built by the guys in Tampa and I was very pleased with the first although on tear down I discovered that dual friction clutch discs are very hard on flywheels.
Kevlar has a higher coeffiecient of friction than the stock disc. I'll always choose the local builder over mass production companies as a result of the many mishaps I've read about on the Fiero forum, the ability to have it built to my specifications as well as several types to choose from for about the same price or less.
Here's a calculator for estimating clutch strength:
http://www.zoomperformance.com/torque_calculator.html
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