O.k. my buddy who traded his 01 H.O. 6-speed 4x4 traded for a 04 600 with a 6-speed 4x4 and was wondering what for performance mods that are readily available for him? and what works the best for the money, any thoughts about the six gun setup or how about propane injection- he is really kickin this idea around! please reply, any round about figures on prices would be nice too!