if i have intake, stock headers, and and aftermarket h pipe, what other things would i need/should i get before cams?

aaaalso.... if i got some mufflers, and had them just on the end of the h pipe so it was fairly short, would that help or hurt hp/tq?

i know iv been askin a few ?'s lately, im just starting to mod my 'stang and dont know everything... yet! haha