Upgrading internals

What you should get depends on how far you want to go. Your crank is typically considered to be good to about 700hp, but the rods and pistons will fail well before that. At a bare minimum, forged pistons, and entry level forged, or Coyote/Boss 302 rods (typically considered to be good to 600hp, and a cheaper option) should be considered. If you want to go faster than that, you'd want a fully forged bottom end (Cobra/Kellogg/Eagle crank, decent H beam or I beam rods and forged pistons).

Clutches are typically rated for a certain power level; you'd likely need a new clutch if you add a significant amount of power.