I bought my truck used and I don't know if the clutch is stock. I think it is. I've towed on extreme and ran it nearly wot and the clutch held. Tow tune is lame and 100 makes it run pretty respectable with great driving manners. I've read that the 100 actually adds at least 100 rwhp on a dyno so that should put a 305 up to ~365 rwhp. I've also read that 100 is about the limit for a stock auto. Extreme is soooo much stronger than 100 - there's no comparison.