got your email....sorry for delayed response having some family problems...yes you have a very similar build to mine...i was never going to put better flowing heads on mine it was built in mind of having a magnacharger on top...with that combo I would think easy 400 at the wheel if not more with a pulley change...
If you still have stock tranny with just a shift kit start saving for a built tranny...it will happen sooner or later and better to be prepaired..
06 silverado CC Volant CAI/ Corsa Sport exhaust
dynatech supermaxx headers/cats
LPE GT2-3 cam/ Comp 918's/ Rods
Eaton LSD 3.73's
IAT Shocks
DANNY TRANNY w/2800 TCS billet verter
275HP and 293TQ Pre Cam
314HP and 303TQ post cam