I broke my falcon 139 tooth after 10,000 miles. What would it entail to switch the rear pulley to the one on the trike, and use the 1 1/8" trike belt?

An interesting question for sure. Assuming your trans sprocket (30T), is a HD one you got from Harley that was originally for the Trike, you already have the wider sprocket needed there.
As to the rear wheel sprocket, I looked at the trike parts list on Ronnies site, and the (trike) rw pulley is 70T. So, assuming your rear pulley is really 68T like mine, right away you would have a lower ratio.............assuming the trike pulley will exchange and fit on your bikes rear wheel and that there are no "clearance" issues...

70T divided by 33T would net you just about the exact same ratio.......So if you wanted to maintain pretty much the same thing as you had after going to the 30t trans sprocket, you would need to find a (wider) 33T trans pulley.

Keep us posted if you are able to get all this to work