18x9.5 +12

I really don't think those front wheels are gonna work out for you with a 285/40/18 on there. In your bottom picture in your first post the outer lip of the rim is well outside the fender lip. In the last one above, remember you'll have 4" of tire above the lip of that rim.

The tires will touch the frame as well. Most of that is the QA1 LCA's don't have steering stops on them like the factory LCA's do to limit the steering angle, you're getting more steering angle than a car with a factory LCA.

My 18x9's are +35. I lose 5mm to my 13" brakes, so, +30 if you're comparing to a 73+ disk brake track width. Even with 275/35/18's my fenders have had the lips rolled and the fender itself pushed out with the lip roller to clear the 275's at the ride height I run. Those 285's will be almost a full 1" further out than my 275's are. They're taller too.

My car sits low and all, but there isn't an extra inch there unless you go higher than factory ride height. And keep in mind the clearance I have is aided by rolling the lip flat, pushing the bottom of the fender corner out almost 2", and pushing the middle of the fender out with the roller. If you look at the bottom two pictures especially you can see my fenders have a convex curve to them where the factory had them flat.

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This isn't even full steering lock in the front. It clears on mine, but not pushed out another inch.
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That first post was before I bored the center hole out. So the wheel actually sits up against the hub now, an inch further in than that last picture of the first post. The 285/35 is the exact same height and top of the tire will be about 5/8” further out than my current setup.
As seen in this picture here.
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The lower corners of my fenders are rusted and cut up, so I won’t have any issues there. If the top of the fender hits, I’ll roll and push them as much as needed.
You can see the hacky fender corners here. (This was before they fit the hub)
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And because the fenders are already like this, I’m not worried about damaging them, or modifying them.

Your car is amazing and it’s awesome you got 275s under the front with such slight modifications.