Through a couple of days of research, I found the answer..

...A 2003 800ho cylinder will not work...It has to be a 2004 to 2007 800 and has to be an ho cylinder. Reason being is they changed the exhaust port after 2003 and made it 0.040 higher. Another way to know if you have a ho cylinder is there will be a " D " stamped on the inside the exhaust port....