Just talking (or typing as it may be) aloud here...
First off, why start out with a Camaro or ZL1 even? By starting at 4000 pounds, you're going to make reaching the 7's that much harder. It's more than okay if the Camaro is what you have chosen but I just wanted to bring that up to start. If you want the Camaro, then case closed.
Secondly, steetable and 7's don't go together (often). Building crazy fast street cars and 7's are two different achievements. Just look at what it takes to run mid 8's in a 3000 pound Corvette (1200+ RWHP + Powerglide transmission + Slicks and skinnies + Roll cage), you're going to have to severely compromise on what most's definition of a street-able car is. 200+ MPH in the half with a 4000 pound Camaro is going to require well over 1600 RWHP, as you can see the C6 in the video above has 1750+ RWHP to hit 205 MPH.
Truthfully, a ZL1 will probably need 1750-2000 RWHP to do 200 in the half reliably. Ditto for consistent 7's.
Blank check 7 Second ZL1 build will likely include:
Iron Block or possibly sleeved or even billet 427+ CI engine from LME/TSP etc.
All forged/titanium/billet parts and internals. Easily $30,000 for a reliable 1500+ HP capable engine.
Custom TT Kit with some big Precision turbos
Holley Dominator
Mechanical driven fuel, monster injectors etc.
Powerglide or similar 2/3/4 speed Transmission with trans-brake, bump box, etc.
Full cage build
Countless small parts from 15" conversion in the rear to parachute etc.
Easily in the $50,000-$100,000 range, all said and done.
And it will never drive on the street with any kind of manners at all. I personally follow RPM's video series and watching Fran's 7.5-7.7 second C6 Corvette race car be maintained/driven is bad enough. Sure, you're not going quite that far, but even taking a few steps back will still be a completely ludicrous street car.
Oh and to answer your question, Vengeance Racing would get my vote. However, all of the shops listed so far in this thread are capable of such madness
.
If you truly have an unlimited budget, by far the best setup in the game for what you're describing is going to be an Underground Racing TT Huracan. Be prepared to pony up though.