Most people would probably not pick that truck for a big TC, it just doesn't have enough payload. The newer ones are better in that regard, older ones would have less payload. Part of the problem is the megacab. If you have it, you probably will be carrying passengers, and they eat up the available payload pretty quickly. The other problem is the bed length. You need to look for a short-bed specific TC to keep the center of gravity ahead of the rear axle. You are probably looking for one that is 1500 lbs or less dry, and 8 feet long on the floor, and that means no tanks or bathroom, usually. I have such a camper (8', 1475 lbs dry, no bath) and I like it a lot, but it sure gets small after a couple of days. I carry in on my 2500 quad cab, which probably has more payload than your 3500 Mega, due to a lighter cab and a Hemi instead of the heavy megacab and the Cummins. I also have a 2WD manual trans - the lightest possible combination, and I picked it for that reason.
Yeah Dodge really screwed the pooch on the payload capacity of those mega cab diesels. None of them have much payload capacity, especially the 2500's and single wheel 3500's. Even the dually mega cab diesel doesn't have much payload, due to such low GVWR.
I have the setup in my sig and love it. Does the Mega have the same 6'+ bed?
I would also do the hallmark Guanela if I wanted the additional 16" length and overhang.
Like the previous poster said, the tc has to be for a shortbed for COG considerations. You didn't mention your payload but I bet it's higher than mine.
I won't offer advice but I'll share information... There are 2 very nice lightly used, shortbed TC's here where we are hanging out... a Lance 2011 850 Gulf breeze Fl and a Lance 845 in Pensacola, Fl... I have seen them both and they are both in excellent condition... like new.
I have a 2008 Bigfoot 2500 9.4 SB on my 2006 Megacab 3500 SRW Cummins. I have upgraded tires and Timbrens on and it hauls it really nice, even with no rear swaybar. To help with sway I extended the overload pads to engaged them sooner (same time as the Timbrens).
2006 Dodge Ram 3500 MegaCab 4x4 CTD 6-speed
2008 Bigfoot 25C9.4SB, Xantrex XADC 60, AM Solar 200 watt SunRunner system, Mach8 Cub, Rigid Industries LED lights
I had a 2010 2500 with airbags, supersprings, roadmaster sway bar and 19.5's. I finaly got the truck where I felt comfortable with the AF 811s.In my opinion the extra length of the cab throws off the cog there is too much weight on the rear of the truck. I even put a heavy bumper and cage on the front with my eu3000 and 10 gallons of gas on it. I use the camper for work and play and I dive alot with the camper off the truck. If you decide to go with the 19.5's go with the lite duty ones. The heavy ones are great with the camper on but even with the air pressure down the truck road like a tank. I wish I would have taken some good advice and got the dually long bed before I spent all the effort and time on the mega. After getting the dually we decided to go to our dealer and throw a 1140 on the truck. The dually has airbags,stable loads and roadmaster sway bar. We will take delivery of our new 1140 in about 2 weeks. The extra weight of the 1140 actually made the truck ride better.
The 811s we have does not have the generator and storage compartments on it so it will fit a 6 or 8 bed.
AF 1140 2 optima yellow tops Honda eu3000 honda eu 2000 companion
2012 Ram 3500 DRW Roadmaster Sway Bar, Airbags, stableloads, superhitch, Buckstop bumper, carli lift, Alcoa's with 3970lb toyo AT's