sportster chain drive conversion for side car

so my build begins. it is a 2005 1200r sportster that I am going to build into and adventure bike. and brock smith of side effects will build the custom off road adventure car. my question is I am going to chain drive and am wondering what sprockets to use. I want to be able to putt around on the forestry service roads and do about 110 k or 70 mph on the highway. Im thinking 23 tooth on the countershaft and 55 on the rear. any input would be of a great help. will end up ordering from zipper performance .