I hear a lot of comments about 1/2 versus 3/4 ton used to tow smaller trailers. I have had 9 different rigs and one has always been bigger than the other until the present Truck camper. i believe most Rv'ers upgrade to a larger rig rather than a smaller unit. I would therefore lean toward a 3/4 ton truck. I'm sure you know as well as I that towing in Colorado is a completely different than towing in Nebraska,Illinois and most any place east of the Rockies. If a 5.4ci will do the job east of the Rockies then you better have at least a 6.0 in this area. As far as weight a 6.0 gas unit will do the trick if you stay with your present TT especially with the 6 speed transmissions. If you are in any way thinking about a larger TT or fiver you need to think diesel. Being under powered in this country is not a good feeling and I've been there a time or two during my 50+ years in Colorado.