Where is the best place to source brake components and wheel bearings and seals for these bigger girls?

When a truck is called a 2 ton or 3 ton, is that it's carrying capacity?

Are the 2 speed diffs reliable units. Do they use the same housing as the single speed units or are they a whole new assembly?
Thanks

Last edited by Digga1111; 02/24/2018 10:17 AM. Reason: So many questions