I have a Roadtrek P190 on a Dodge chassis with the 5.2L/318. Currently it has 92K miles on it. I travel both with and without a 10' enclosed utility trailer which is 1,400 empty, probably close to 2,700 full. The 3500 and 5.2L/318 does a great job and I haven't had any issues with it over the last 30K+ miles I've owned it. It pulls the trailer well and I never feel its struggling except for steep mountain grades. Most normal grades I can travel uphill at 55-65mph without feeling like my foot is in the carburetor. I can tell the trailer is there, but don't feel like I am pushing the engine hard.
Trailering isn't the same as having that weight on the chassis, but I wouldn't worry about the extra weight on the choices you've outlined. The Roadtrek on the 3500 chassis with the 5.2L/318 is well matched in my opinion,