Guys here is what i remember.
Me and Al used to run 116-117 MPH with only exhust & chip.
No port work
With plenum/IH porting we were running 119-120.
So my opinion, you guys are looking for cake and eat it too.
The LT5 likes to breathe.
Heck even GM knows you can't have your cake and eat it,have you guys heard the LS7 at WOT crappy/loud from outside the car.
Also if GM went with full 3" exhaust with flappers for 500 HP why would you guys go with 2.5" and down to 2 1/4" (Corsa Tailpipe)
Think of this for a minute if your exhaust is restricted porting the heads won't be worth it you'll go from 116 to maybe 118. or from 370 rwhp to 390-400rwhp that tells me your exhaust is robbing you of 25-40rwhp.
Anyway food for thought.
Pete