Mine is a '96 2500 and the original owner went to great lengths to explain how he had to wait several months to get it because he ordered it with "one-ton 3500" springs. Whether any of that is accurate I don't know. It has the 241DLD t-case, nv4500, and D80 rear. So I don't think there is much "heavy-duty" about it due to the light-duty t-case, which continues to work fine.
I do use a Boss V snowplow and run larger 285R-16 tires with no problems. My truck does not seem to suffer from the front end sag that many guys claim is the reason to install spring spacers. They would make my frontend higher than the rear.
As for the I-beam crossmember, I think that would be redundant given the massive frame mount the Boss V uses and it's square tube crossmember. More so now that I have purchased the steering box brace from Solid Steel.
I would not worry about either the 2500 or the 3500 frames' abilities to support a snowplow or hold up to the abuse. My only worry has always been the doggone airbag... Hitting concrete parking bumpers and similar under the snow always makes me cringe. .