i dont think you can put a n64 inside a normal xbox case....
also you may want to think about all this gaming in your car... your driving, your not really going to play games that much unless your stopped. Ya its cool for passenger, but if all they do it play games it might get distracting. If it was me, i could havea computer with alot of emulators, and have a inverter so i could plug in a xbox whenver i wanted and take it out whenever.
Thats just my 2 cents
p.s. it sounds cool tho