Altough, I might have found a golden goose right among the starting cars cuz it's at lvl 250 and is already fully capable of defeatin' that Porsche.
This comment is just for fun...
In the real world, you'd have to spend so much money making the Camaro a 'restomod' if you wanted it to be able to outrun a modern 911. The Camaro, while 'small for its day' (an answer to the 'pony car' market), did not handle well by modern standards.
Heck, it (and the first four generations of it) came with a solid axle rearend, drum brakes, bias-ply tires, etc...
(I do like the wide-body look on the one you have in the game.)
The extra HP in your game version is also going to help. They originally shipped with a maximum of 375 HP (from the 396 ci version of the SS). The SS versions came with a 350 ci engine that put out a claimed 300 HP, though it also came with a heavier suspension and disc brakes on the front (with drum brakes on the rear).
I can't tell which exact 911 is in your picture, but it looks like a GT2 or GT3 model -- maybe a GT3 RS (which are amazing). The GT2 RS is also amazing.
If it's a modern GT3 RS, it's going to do 0 to 60 (0 to 100 km/hr) in about 3 seconds. It has an LA of about 1.3, so it will take a lot of g-force to lose traction in corners.
That's something you'll have a hard time beating with a Camaro SS, even if you've gone through the whole restomod process.
In the real world, you'd do well starting with a 6 gen Camaro. There's the ZL1, which is easy to modify for higher outputs. Then, if you want to go wild, there's the 1LE Extreme Track Package. That too will take an aggressive tune and not explode.
In the real world, you can get a pristine 1969 Camaro SS (with the 396 ci engine) for about $150k. It'd cost you (at least) twice that to modify it to the point where it could keep up with a modern 911
You can get a pristine 1LE Extreme for under $100k. If you have the patience, you can get one for less than that at auction.
Also, a 911 GT3 RS is going to cost about $250k, but you'll likely spend more than that adding options. It'd still be less expensive (and less of a hassle) than it'd be to modify the old Camaro. Plus, it comes with a warranty!
Again, this is just for fun. It should not be seen as serious content.