When I replace the passengers side from 9 to 7 I got the base from
shop4seats.com was very happy with it. My wife likes the difference, sorry can not help on trading, but do have an extra 9 if someone needs
Retired and never looked back
Just for info. I have a Freedom Elite 22FE that doesn't have swivel seats. Replaced passenger seat with swivel base. Now at least that seat can swivel, giving extra seat when camped. Easy bolt in install and nice to have an additional seat facing inside when camped.