139t
The 139t belt fit my gear change perfectly.
32t front pulley HD #40659-06
139t belt HD #40040-05
There are aftermarket pulleys and belts that will work as well. As mentioned above, the trike section has a lot of good into. A search for gear changing yielded a lot of helpful info as well.
The gearing change made my barge very nice for 'town touring'... the difference is very noticeable.
Made about 250rpm difference cruising at 80mph. Last day trip 2-up mixed city, rural, freeway yielded nearly 45mpg.... YMMV...