Kolele steels and redline clutches are the common upgrade, get away from the plastic accumulators and servo pistons if you so desire. Also there is a posting on here for the 32rh, it has some good sonnax info and moparts forum in the for sale section has performance parts for the 904 that is the same as the 32rh. Ymmv. TimI would also find out about seeing if you can use different clutches? On some autos you can use thinner clutches for more.
And see what different RPM's of torque converters you can get.