I hope the sound you are looking for isn't related to high RPM engines. As you know, the LS gives a great sound, but it is the deeper rumble. I have CATs that feed directly into 12" Flowmasters that then exit to the side. It sounds really wicked.
If I were building again... I would install the LS7. I have the LS3/480. Fran said the cam in the 525 made it tough for street driving. I wish I had the 525 or better yet the LS7. I will eventually have mine turbocharged.
A question... when placing interior carpet, dynomat material is placed first (noise). Does the carpet go directly on that or is there a intermediate material?
FYI- I had an issue with car dying when coming to a stop. Then several times the throttle pedal would not work at all. Shut down a nd...