The 904 I have before we put in the alumium drums it had all stock parts other than being rollerized and high gear spring pack. Our 60 foots were 1.24 to 1.30 in a 3100 lbs car. The only thing we broke was direct drum broke after 600 pass on it. The shakt just broke out of the center of the drum. Has griner brake in trans too. Where I get parts machined for my trans. He say they are good for 1000hp with good parts in them. But didn't see much improvement in et with direct and high gear alumium drums.