I agree. 50lbs on an F350 is splitting hairs, and if it's going to make or break you, you've got bigger problems. I'm one of those guys who thinks that if the camping stuff starts intruding into the cab, I'm bringing too much along and really should rethink what I bring.
I'm just a weekend, 4 days max, type of camper, though. There are people who set out for weeks at a time and it just isn't practical to cram everything into the camper.
Pulling the seats will give you quite a bit more space, but beware of the "hump." The floor under the seat isn't flat, so you will either need the exact right "stuff" to give you a full-width flat area, or you'll need to build a platform.