What is the difference between these models, mechanically? I can't find a good source online.
I know that the 3500 is rated with a higher GVWR capacity, etc.... but what is mechanically different about these models. Since they can all take the largest engine (5.9L) and presumable have the same transmission... It just seems weird that they are marketed so differently.

 

The differences are in the suspension/brakes. The 'heavier' models use higher spring rates, heavier duty parts, larger brakes, etc. Aside from that, there is no practical differences. (perhaps available options? like gear ratios??)

 

That's interesting that they market these so differently but practically are so similar. I would have expected at least some frame difference.

Is it safe to say that you could get a 1500 and upgrade components to make it identical to a 3500?

 

Probably. The bolt-on subframes *might* be different, but, not sure on that.

Keep in mind though, that it just doesn't matter what you do to it, you are still legally restricted to towing/hauling capability of a 1500.....