heavy 2500 specs

i have a '91 C2500 Silverado. i have been told that it's a special 'heavy 3/4' because it has the following:

4L80E trans (first year offered)
14 bolt rear w/ 10.5" ring gear
8 lug 16" wheels
'supposed' 1 ton suspension

the truck has the original 350 and nothing has been messed with to my knowledge. could someone give me the technical name for this package and some more info as to why it is different from an actual 3500? the title says 'GMT-400' under model.

One thing I have noticed with Chevys/GMC from, oh, 1981, is all smallblock 3/4 and one-tons have the smaller 14-bolt from the factory. Not to say you couldn't order or change it out (it has the 9 1/2 " ring gear and is a semi-floater vs. the full-floater with 10 1/2" ring gear) I have two of these rear axles and wish I had the full-floater! Check your GVW on the door post--should say something like "8600 GVW" (3/4 ton)