I am currently building a 440 Ls7 that should make around 630rwhp N/A and around 850rwhp on spray to get me into the very low nines at full weight.
These numbers are based on open headeds at the track and will be tuned with open headers.
For the street i will be running a 3.5" ORY and Corsa catback. The ORY will be V-band clamped to the headers. Should only take me a near 10 minutes to take off at the drag track. LS2bait's idea!

With that full exhaust what kind of power am i looking at, i know its much more restrictive than open headers that will be dumped.
Guessing this kind of a question is a shot in the dark... But its worth a shot.

 

Could lose quite a bit. With it tuned on open headers, I'd bet you lose 40-50 peak hp.
You could always put in a couple of QTP electric cut outs for when you wanna romp on it on the street.

 

Mostly going to be a factor with the type of muffler(s) you decide to run. V-band is nice, I have that on my longtubes as well, previous owner of the LT's had it done that way to expedite the movement from mild to loud