One of the stroker kits from supersix motorsports would probably get you up towards 275hp. Bump the compression and some 93 octane, you could maybe see 300 horses.
Of course, you'd need all of their other goodies. Like race-prepped heads, sheetmetal intake, ported lower, cam, etc.
If you're in an automatic, you'll probably need a stall converter since the rpms would be shifted slightly upwards. Without it, you're car will die everytime you stop.
The 7.5" rear end uses the exact same axles as the 8.8. The weak component is the differential. Get a good trak-loc and it'll hold.
I'm not sure, but I'm going to go ahead and say it's going to be difficult to get this to pass emissions if there's a sniffer.