01-03 2500 and 1500hd are the same basic truck 8600lb GVWR. The 2500 is available as a regular cab, or an extended cab. The 1500HD is only available as a crew cab. It was a marketing deal to call it a 1500hd. For 2004 it is called a 2500 CrewCab. There is a 1500 CrewCab being releases. It will use 1/2 ton components and have the same wheelbase (143 inch) as an extended cab. The bed will be shorter than the current short bed. (like a Ford Super Crew)
The 2500HD 9200 GVWR has a heavier frame as well as mounting the body higher. The standard powertrain is a 6.0 the same as the LD. With the 8.1 or Dmax you get a bigger (10.5 inch) rear end and Full Floater rear axle. I don’t believe the 6.0 has the FF. I believe it is a 9.5 inch on the 6.0 HD. I know the 2500LD uses a 9.5.
As already mentioned the frame is bigger on the HDs and 2500s use the same transmissions as the 2500HD 6.0s. 2500 autos get the 9.5 semi-floater rear axle but, 2500 5speeds get the 10.5 full-floating rear. All 6.0 2500HDs get the 10.5 rear and 8.1/6.6 trucks get the 11.5 rear. Hope this is what you were looking for.
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