[bigfour]

Nice bike, I don't have a reccomendation for a good exhaust but from personal experience, a straight pipe would do real well on this bike as long as you've got the carb set up right. I cut off the exhaust on my bike and it sounds real good--a nostalgic roar, nothing a cop will pull you over for.
For now, I've put a restictor cap on my exhaust to provide a little backpressure until I've got the carb fine tuned. If your bike runs good with the exhaust drilled out that much, you might not even need to make any adjustments moving up to a freer flowing exhaust.