how much horsepower can the 904 take?

crackedback said
You really don't need a fancy or expensive front drum in a 904. They don't detonate like the 727 units do because they are smaller in diameter.

I agree it's not needed for the strength of the drum but I bought mine for the relocated snap ring groove that allows for 5 of the thicker red frictions { they claim it will hold up to six frictions but they must mean the thinner stock type } and that it was sold as a kit with the 24 spring return module and the piston designed for the module