I don't have the info in front of me, but if you can get the horsepower rating at an RPM just cut that RPM number in half and drive around at that. Quick internet search said 6250 rpm, not sure if the 600 has an RPM limiter. So buzz around at 3100 or so, might be kind of slow though.
Just avoid overheating, as that can cause the oil to glaze on the cylinder walls and prevent the rings from seating.
Rick