Often, we have to consider the source.
JIMNLIN's link is the official Ram bodybuilder guide.
It's very specific that the frames are the same, and it's from the manufacturer of the vehicles.
45Ricochet, the links you posted are third-party and are vague.
The Allpar article linked in the CumminsForum thread is also vague, but it does state:
For 2013, Ram Heavy Duty trucks are using new frames, built with high-strength 50 KSI steel, to increase stiffness, improving noise reduction, ride, and handling.
The Ram 2500 and 3500 are "Ram Heavy Duty" trucks, and notice no mention of frame differences.