Hotbutta, I am pretty careful on my exhaust temp.  I haven't seen over 1100 F during wide open throttle but all I have been riding is flat hard black dirt.  Usually shift through all 5 gears and hold it open in 5th for a little bit.  I will find out this spring on the sand dunes with paddles and good traction.  Q2W, I don't know anything about a number on the bottom end?  I haven't had the cases split so I am just assuming that it has the 88 to 90 4th and 5th gears.