Dual stage reeds, for crisper throttle response.
A decent (straight through) silencer, for less back pressure.
Reed spacer block between the reeds and the jug. Will give a little more oomph down low with the Fatty.
A free +4 timing advance, for even more low/mids with the Fatty
Take the lid off the air box, or modify by drilling holes, even more oomph over the whole range.
Use a uni filter directly on the throat of the carby, or on an extension tube, even more oomph.
Be wary though, every change you make in the breathing, on the exhaust or the carb side will require that you increase the size of the main jet.
Plug chops will need to be done to make sure that the jetting is correct..
Do heaps of reading on the forum, there is a multitude of great advice here.