You can put the rear seats in a J400/J430 and it's still registerable as RA-Aus if the rear seatbelts are removed prior to DE-Registration and transfer to RA-Aus. Unless you're the original builder there's no going back.
Jabawocky loves his J430. It has more usable load than a Cirrus SR 20 and with the upgrade to 750mtow, will lift craploads more.