Brakes are the same from a 2500 to 3500 SRW.
3500 SRW MAY have a bigger axle, although I doubt it. Driveshafts and transmissions are the same.
Heavier coils and adding airbags have exactly the same effect.
3500 have leaf springs instead of control arms and coils. Leaf springs are considered a heavier duty offering but do sacrifice ride quality a bit compared to the 4 link and coils.
The only thing you can not change is the LEGAL GVWR because you are taxed (registration) based on that. It would take an act of god to upgrade that, at least in my state. We can freely downgrade GVWR to save on registration, but can never upgrade so far as I am aware.
Put your airbags on it like the 10 million folks before you have done and move on with life. Stay away from this subject on forums and you'll be happy.