Having been a team owner that raced a VR1000 and Buells in the Lightning series, as well as Anthony Gobert's Muzzy superbike and several other GSXRs and FZRs over the years, my best advice is to buy a used XB9R, with a race kit if you can find it, and then go race it.
A chain conversion ($ 1,250 approx) will be worth it's weight in gold. IF you don't do anything stupid to the motor, (meaning keep it relatively stock inside), and don't try to run it at 10 grand, you will have a relatively reliable racebike, and parts are cheap. You can do an engine rebuild on a Buell (XL1200 series) for about $ 120.00 including pistons, rings, & gaskets. If you do the work yourself.
Buell engines are much simpler to work on than overhead cam engines, and contrary to popular belief, (those who haven't actually raced them) they are reliable if you don't overev them substantially.
Also remember, dyno's don't win races, riders do. In the amateur classes, 5 or 10 hp is not going to matter much. Don't get caught up in the "More motor is faster lap" crud. That just costs money and grief. You go to race, not work on racebike at track. Keep it close to stock. Use stock pegs, bars, etc. They are cheap, and you can keep spares. Trick parts are great until you break them.
I have a friend (Chris R) that is 600 class champion in endurance racing, and went from an R6 to an SV650, and went 2 seconds a lap faster at Texas World Speedway, due to a LESS POWERFUL engine. he had more time to actually think about what he was doing.
Besides, go racing, have fun, learn, and feel good about it!
Buy the Buell. You won't regret it.
They are not much more initial cost to purchase, as used ones are going for $ 4,500 - $ 6,500 since the 12R came out.
Best of luck.