Lots of tires of various sizes are available for use up to 149 mph, and I know some people are using them at higher speeds. But for the widest selection, I would (did) build for 17" tires because there are endless choices for the highest speed rating, so you don't have to upgrade to go faster. You can probably even find good used ones from sport bike riders as long as there's some tread left and tires are not old (sport bike riders usually wear out tires in months rather than years). Also, after pinching a few tubes in my time while mounting tires (especially "Z" rated ones which are stiff as heck), I wondered how many I almost pinched---that could fail at any time. So I converted to aluminum rims for peace of mind. Aluminum rims are truer as well, so you eliminate runout. I use a 110/70 ZR17 on the front and a 120/70 ZR17 on the rear, which is also a front tire, so I run it backwards. No problems up to 145mph. Traction should not be an issue with the kind of hp you'll have and the 2 mile run up to speed. If you get over 175mph, you can use the international course with 5 mile run up. Not to mention names on here (I ran into one situation where one craftsman took exception my mentioning his name on the forum!), there is a certain 750/1000cc pushrod Triumph Trident that achieved 200mph this year naturally aspirated, so it can be done.
