I assume your asking 2500 vs 3500 SRW.
Dodge/Ram Body Builders Guide shows the frame rails (2500/3500 SRW) are the same even with the coil spring 2500 truck (same cab and bed) back to the coil spring area. The rear of the frames rails are modded and have componentry added for the rear coil suspension setup.
The front axles are the same on both trucks.
Brakes ??
Dodge/Ram body builder guide doesn't give us much info on brakes sizes but Dodge/Ram dealer mechanics and behind counter sales say they have the same parts numbers. Rear axle assy is the same 11.5" AAM on the 2500/3500 SRW.
One member (IB516) says this about his 2500 coil spring Ram;
"I hooked a 14k 5er to my coil sprung 2500 and it sat level. I regularly towed a 12k 5er with no issues. In fact, the 2014 2500 with coils sagged less with the same 5er than my 2007 3500 SRW did with Torklift Stableloads installed."