Here is a link to some axle identification info. If you look around you can find lots of info online with some simple google queries: http://www.therangerstation.com/tech_library/Dana44.htm
I didn't see any mention of lug nut count, so just in case: 6 = 100 and 8 = 200
If the truck is from the forestry service any number of things could be going on. I bought a '67 c20 (yes bow tie) that had been a forestry truck. The id said it was a six with a utility bed but it had an eight and a full bed. I think the guys at the garages just swap in any parts they have laying around. The trucks in the forestry service take quite a beating so they just do as needed. It would be a good idea to check both vins to see if they match. You never know if someone dropped a tree on the cab and they just swapped it from another truck. Just a thought.