The only difference I've seen in the 2500 to 3500 springs is the 3500 has one more helper spring. The big difference in the 2500 to 3500 is your wheel bearings. Why they would call a truck "HD" and put 3500 springs on it and then put on whimpy bearings instead of "HD" wheel bearings like the 3500. Bean counters I suppose.

I've had airbags on my truck for awhile now. You find the sweet spot where your not loading to much on the front and get it up in the back and it does alright. You get it loaded enough on the back and air it up and you'll start putting more weight on the front axle and it can act a fool when hitting bumps and things. If you can afford the compressor and in cab controls that would be handy. I keep wanting to pick them up so I can adjust as needed anywhere I may find myself, but for now it's just using the compressor at home or a foot pump from wally world.

 

Are the bearings any different? The rear ends are the same...

 

When I ordered my warp proof EBC Front disk rotors there was a part number change between the Front Dana 60 2500 and 3500, and some (mine) automatic 2500's came with a Dana 70 in the rear rather than the 80