The Ram SB will probably work fine for that camper but if you haven't bought the truck yet I would Seriously consider a longbed.
As you mentioned, the Ram bed is only 6'4 and it has a pretty good curve in the front of the bed that pushes the camper back even further.
I loved my 15 Ram but sold it and just picked up my 16 LB today. I'm going to a 5th wheel TH and didn't want to worry about a slider hitch. I'm sure I'll get another TC someday and a LB allows many more options.
The LB rides better and really isn't any harder to maneuver. Just 22" more tail.
It also gives you 600 lb more payload.
With a SRW you could probably go with a 9-10' camper with a slide and have much more room. Look at the Arctic Fox 990 or maybe a Lance 950S.
