Basic up grades:
CAI - KKM high rev unit & K&N
Exhaust _ Borla, Magnaflow, Bassani, or custom made system
ECU flash - XCAL with tunes by Torre
That's about all you can really do without going into a few $1000 in major upgrades. Even then, your limited on choices.
Handling options are out there.
Brakes options a lot to choose from.
Exterior, your limited. Razzi, Duraflex Racer, Wings West(if you can even find one), 1st or 2nd gen LSE(getting very hard to find)
No one site will have this stuff. Your will need to search for it. We do have a LOT of info here. But searching for it through a ton of worthless threads does make it difficult. Pinned topic "LS Info.... Wheels, etc" has a lot of useful info. Try there for some of what you might be looking for.