Man, when someone literally, intentionally starts a brand war and can't even get a bite, but a weight war breaks out instead.....
I'll go out in a limb and say if billtex has been hauling the 850 on a now 14 year old short bed srw diesel, he couldn't give 2 shts what anyone thinks about him hauling the same camper on a brand new 1 ton long bed srw gasser. Ain't that what you weight cops preach? Diesels eat up the payload for the camper? (They don't, but that's what y'all think...)
To the OP, and this is painful to say, GeeEmm 6.6 will be a brand new power plant. I'd give it a year or just go for the Ford or the Hemi. At least you'll be able to get more than 6 forward gears with the Blue Oval or the Ram.