Marm's already provided the same answer above as I was composing this...

Given that a quick Google search for 1:18 scale Chiron and R8 shows that production die-cast models are already available why are you reinventing the wheel?

https://youtu.be/QQCDGUZvknQ

Companies like Bburago, Maisto, AutoArt & Kyosho probably spend a couple months of work-hours to reproduce every last detail in a model (whether via CAD or old-school carving). Leveraging the economies of scale in mass-production, they're able to then manufacture all the details that go into a die-cast model... interior pieces, clear windshields, real rubber tires, chrome wheels. They avoid the massive lawsuit by going to the respective car manufacturers to $ecure licensing. All that development money gets recouped (maybe) when they sell that model through hobby stores, toy stores, department stores, and the gift counter at the car dealer. The consumer pays a relatively low price ($40-$100) for something that has a reasonably high amount of detail AND with the proper/faithful array of materials.

The TurboSquid file previously mentioned is likely aimed for visual-effects only and for certain wasn't modeled with working hinges or parametric moveable parts. You're basically asking someone out here to spend the level of time and engineering effort to create a (produced, existing) model in CAD so that it could be 3D printed with a single homogenous material?

This again begs re-asking the question of why. Because you're trying to out-do Bburago and want a Chiron with an opening engine bay? Because their body paint combo isn't to your liking? The die-cast industry probably spends at least $10,000-$30,000 on replication and prototyping alone for each model. Do you have a checkbook or willingness to match that? That's what it'll take to reach the level of detail you claim you want.

In the landscape of personal manufacturing, 3D prototyping & CAD design, it's entirely worthwhile to spend the time, money and energy to create something new, something that previously didn't exist. If you're doing this out of whimsy for a minor change, it's a foolish pursuit.

A less eccentric approach would be to buy a half-dozen of the same die-cast model, designate 2 samples as the project and the others become donor bodies. You're now able to cut out the trunk and gas cap that wouldn't open and use cannibalized parts to re-fit into functioning versions of the project car. Lots simpler to 3D print and cast working hinges & mechanisms only where needed. Jewelry TIG welder could be used to connect hardware to the donor parts & panels. Wrap up by giving the reassembled body a custom paint job using factory paints and clear coats of your choice... that is, if you're pursuing this for personal enjoyment.

If however, the choice of mentioning "partnership" in your title is suggesting an aim of taking this to an industrial level, I hope you're prepared to take care of all the licensing and tooling costs. The $30k paid to scratch-model all the prototype parts will be a bargain compared to all the additional expenditures to produce a worthy line to compete with the major players out there. Is there room for someone better to elbow their way in? Of course. A higher-level of sharp, crisp detail hasn't been reached yet. And none of the major players have incorporated lighting effects (functional headlamps, turn signals, illuminated dash cluster)