The RB is cool. I'd go cheap if I were you though. It's not like you're making 500lb/ft of torque. Look around and see what's cheap. Get it running and save money for tires. If you can find a flywheel and counter weight cheaper than a clutch kit I'll give you my clutch and pressure plate.
And I quote,"a straight mandrel bent pipe." If it's straight it sure ain't bent!

No one does mandrel bending around here. I've checked. Get the header and the cat from James. We'll find a place to hook you up and then we'll have a test pipe made to replace the cat or just run the gutted cat that James has.
For mufflers, I hate to say it but, you might want to look at Flowmasters. I think it's the 60 series that is supposed to be the quitest. The reason I say them is that they have no glass packing to burn up. I'd hate to ee you burn out a muffler in a couple weeks and not be allowed to race.
Chris