Shit dude, my little Greddy kit pushing 8 psi and ~215 whp will run low 14s/high 13s. Keep in mind that is with a GSR motor. You don't need 25 psi to get those sort of times. A RevHard or Drag kit with a T3/T4 hybrid turbo will easily get you those sort of times without going over 10 psi on your LS motor. I would put in some low compression pistons and rods since you are rebuilding it anyway so you can handle extra boost down the road if you so choose.