I feel like the obs trucks were large inside at least they felt to me to have the largest back seat. I haven't owned one, but have ridden in a CC plenty of times. I've personally owned an 01 & 04 crew cab Ford and felt they were larger inside then my 2012 ram 3500.
4r will be the easiest to make work well. Any of the superdutys are nice for room and are a big step up from an obs truck in overall comfort and driveability in my opinion.
10.4 My last fummins was a 01 F-350 with the 4R100. I never got the tranny tuned right and hated the stack shifting it was doing so I put a nv4500 in it and eventually sold it. I hope to have more patients this time around!
you are technically correct however; 5Rs still have a mind of their own and refuse to shift identically under identical conditions so it can cause frustration for OCD people.