The car looks unreal! love the garage too! I'd recommend the 4.7, makes a nice difference and doesnt make it too bad on motorways!
Your harnesses though, they way they are currently set up there's a good chance they would make the seat collapse in a crash. Also the angle the straps go down to the floor will compress your back if the seat doesn't collapse. Neither of these out comes are good! And i am speaking from first hand experience, a good mate of mine couldn't move his legs for two days after a crash due to spinal shock from the harness angle!