I recently got rid of my horrible 2006 6.0 F350 CC and got a 2018 CC. I really like it and Ford did some nice stuff. But I need to have the rear seats up generally. On the old one my rifle fit aft of the seats which folded down. No longer possible. Does anyone have a workable suggestion on where they put one?

Take a look at this, it may be similar on your truck for getting the rear seat down. https://m.youtube.com/watch?v=...Ib8&feature=youtu.be

My 16 F250 has seats that are probably similar to your old truck.

I can definitely fold the back seats down on my '16 F150 SCrew. The passenger side has a release for access to the back & tire wrench.
The drivers seat, is a bit more difficult. Have to reach behind for it. There's a few solutions to make it simpler from DIY to aftermarket.

Also, something like a lockable tuffy box that fits under the seat could work.

As posted in the YouTube video above, Builtright makes a release for the driver's side rea setback. I've got one on my 2015 F-150.

https://www.builtrightind.com/...50-rear-seat-release

I like the metal lock boxes that go under the rear seats myself. More secure storage than just tossing it behind the seat.

Obviously too late now, but that is the main reason I have been looking at Dodge Mega Cabs. The mega cab is a crew cab, plus an additional 6" - 8" of room behind the rear seat. Unfortunately, only available on 3/4 ton starting in 2009 model year.

I think the Ram Mega Cabs started in 2005 or 2006.