i think...you should... make a baja version :] but make it a little smaller. i dont think fj cruisers way over 4000 kilograms and are longer than 10 meters. but everything else looks good. really good job on the body.
What i have to say is that: for the soft tires, to change that, just change the density. Scale it down a little. make it a little heavier (this will also make the suspension less stiff). and also, to make all the stuff collide with A just make whatever you dont want to collide put on "no self collision" this will make your car not collide with the wheels along with making it all collide with all the ground and everything. if that makes any sense. hah.