Exhaust, tune and cai questions...

[dbs1]

I'm still thinking of owning one of these critters again and have a few questions.

How much would I gain from a catback vs just replacing the stock mufflers with some better flowing ones like magna flow?
What kind of gains can I see with a good dyne tune, exhaust and cai?

I'm hoping to find a 6 speed and also throw on some 4.10's. I don't think an sc or cam swap is in the cards, but I'd like to see 450hp at the crank.

Also-has anyone put the SSR body on a SS trailblazer with the awd and some air bags to raise it up and down? I'd pay an extra $5 for that.