check if the 6th gen V6 knuckles/bearings are the same size as the 4 cylinders. If they are, simply swap the V6 5-lug hubs onto your bearings, along w/ the rotors and matching caliper/brackets and there you go. 5 lug conversion.

and... speed is probably not limited by his wheel size... bigger/heavier wheels would probably cause him to accelerate slower, taking longer to reach speed, but it doesnt keep him from driving fast.... and conversely, i believe heavier wheels would increase stopping distances? not to mention having like no sidewall isn't a nice thing either... do 19/20 inch low profile tires even support enough weight to safely hold up the car???