what i can do to change my thunder bird's firing

i have thunderbird bike (Tbird Royal enfield,350 cc, AVL engine, petrol ofcourse)

and i want to change its firing, i want to make a chopper from it so is it possible to give it a firing like hearly davidson???

what is a silencer's internal structure?
i know that in bikes, baffel type and glasswool type.
but i dont know which part i have to change or modify....