To achieve roughly the same ratio while changing the rear sprocket instead of the front, you would need to add 4 or 5 teeth to the rear versus subtracting 2 from the front. I'm not aware of any 72 or 73 tooth one inch rear sprockets that will fit a late model Harley, and of course you would need a 4 tooth longer belt that probably doesn't exist either.
32 tooth front, 68 tooth rear, 2.125 ratio (standard)
30 tooth front, 68 tooth rear, 2.267 ratio
32 tooth front, 73 tooth rear, 2.281 ratio
32 tooth front, 72 tooth rear, 2.250 ratio
On another note, changing the primary ratio will also allow you to change the overall gear ratio, and it will do so without affecting the speedometer reading like the changes to the trans output sprocket will. But changing the ratio in the primary will affect the rpm versus speed sensor reading that the ECM utilizes for things like the 6th gear indicator light, and possibly the cruise control. I seem to remember some folks reporting problems with those items after changing to a different comp sprocket a few years back. It would be a good idea to research this thoroughly to see what negative affects it might have before tearing into the primary and changing a bunch of parts. Just a thought.
Jerry