Might be mistaken but I do believe there is a difference between 2500 and 3500 SRW chevy trucks, at least in the rear suspension. The front is IFS in both. The 3500 SRW GVWR is like 11,400# vs the 2500 at 10,000#. This comes from a 3 stage rear leaf spring in the 3500 vs the 2 stage in the 2500. The chassis of the 3500 SRW is identical to that of the 3500 dually including suspension, but the 3500 dually has the additional capacity of 2 more rear tires.