Look deep inside and ask yourself "am I going to pay large amounts of $ to add power to a 10 year old v6 to the point it's going to need an 8.8 rear?"
If yes, find an 8.8
If no, you're going to be fine with the 7.5. If you're going to end up adding just a few boltons there's no point to getting an 8.8, the power your car will make won't be close to needing a stronger rear end.
"Joey" 2004 v6: SR CAI, MPT Tuned, 4.10 gears