You probably COULD get a body lift but there are things that will get in the way.
First, and this isn't just an old bastard trying to make sure you're behaving yourself - make sure it's legal. If you have an accident - and even if it is NOT your fault - you could end up paying for it, if your car is found to be unroadworthy (because an unroadworthy car shouldn't have been on the road).
Second, the air bag system shouldn't be compromised. I didn't think adding a block under the cabin would create a big deal with that - the air bag system should still function, but you need to make sure that you don't disconnect it.
Third, there are a few physical changes that need to happen to get a large amount of lift. Brake lines and ABS lines are the first and probably most important things to take care of. Then there's radiator height + possible new hosing, as well as air conditioner, front-mount intercooler, transmission cooler - all these things MAY have to be adjusted.
As for tyre sizes ... there are quite a few threads discussing what size tyres you can squeeze in. Your 285's might also need to have the plastic inner guard behind the front wheels manipulated with a heat gun.
Also, be aware that your odometer will be out. Don't worry about the speedo, get yourself a GPS and use THAT for speed measurement. When you're working out fuel economy, your km travelled will be out significantly.
