The lower you go on the spur the more top end you will get. The the lower you go on the clutch bell the more bottom end you will have. The higher you go on the spur will increase bottom end but in small amounts. The higher you go on the clutch bell will raise the top end but it is a bigger change. For a big change, change the clutch, for a small change change the spur.
By going to a 70 tooth spur with slightly increase top end