I was wondering what gears I should install on my 2000 Powder Special 600 for the type of riding I do in Saskatchewan, flatland. The gears that came with the sled only let me go 80mph at 8000rpm. I was thinking of putting ZR 600 gears in it.
Any help would be appreciated.

You probably do not want to go quite as tall as ZR gears because the wieght of the track. A good start would be 2 teeth lower than the ZR