The down side to the 63 mm wheel is it is very violent when it spools up. The 66 tames it down. My turbo was a TE-63 large housing 3 bolt. I could not stage the car on the foot brake and control boost at the line at all. As soon as the boost gage started to move it would go to 25. Nothing in between. John Craig put the 66 wheel in it and now it is cotrollable. That is the reason the 45A was the big wheel. If your goig to try to run on street tires you don't want a turbo that hits that hard. Call John and talk to him before you make this decission. Hope this helps