The capacity of the axle is exclusive of the GVW. The GVW is the weight of the vehicle plus it's maximum payload, including passengers and fuel.
Your 48 with an 8800 lb GVW was at the top of the ratings for a 1 ton truck, that being said, an HO72 would still have been the axle it shipped with, and it would have been the same axle that shipped with a C30 in the 60's and 70's, with minor mechanical differences within the carrier assembly.
I can't tell you for certain what the capacities refer to but my guess is that you may drive yourself nuts if you over think it. Understand that all things being equal, if you put a 4.10/4.11 differential into an HO72, you are in effect derating that vehicle's carrying/pulling capacity. 8800 lbs would probably technically be incorrect after that swap. Also understand that the spring packs, as well as tires and wheels also factored into that GVW rating of 8800 lbs.
The bearings will have numbers on on them you can use to source new ones.
Does that answer your question?
