Shift improver--for more pressure.
More clutches where possible.
Better torque converter--tighter!

My opinion, MOST do not need a multi disc converter when the VB is set up right.

Stock pressures are too low for about every application.

If a diesel application and much more torque is added--over 400hp-- a good input shaft is a must. If you don't you risk breaking it and a full rebuild will be needed.