If you want to find something that will rear face a long time weight limit shouldn't be your determining factor. The vast majority of kids will hit height limits for seats light years before approaching the weight limit, so you definitely want a taller shelled seat.
Your situation is fairly unique, so I would actually recommend posting on car-seat.org. You don't need to create an account to post there, although without an acct it takes time for the post to go through a moderator before being visible. That site is basically staffed by techs from around the country (and several international people as well) so they would be better equipped to answer such a specific question based on your specific vehicle.
Good luck and hope this helps you!