From someone who has replaced a couple of dozen clutches, the Stillen would actually be our last choice. The OEM clutch is a very good clutch at a reasonable price point (so far) and obviously the fitment is perfect. The OEM clutch works very well in any GT where RWHP is at below ~750. Next up for us would be the clutches from Spec. They have 4 different clutches for the GT - each for different horsepower levels. As you shop a clutch for higher HP levels, you get improved clamping force but at the expense of a higher clutch effort and a little trickier engagement feel. The spec clutch fitment has always been like OEM for us. Finally, the Stillen clutch is similar to OEM in HP limitations but unlike OEM and Spec, there were funky spacers/adapters for the throwout bearing to adapt it to a GT application. With the OEM for stock to 750RWHP and several Spec clutches to choose from - none requiring adapters for the GT, we stopped recommending/installing the Stillen clutches a decade ago.