I did a little more research and I don't see the 8-lug floating axle as an option for the 3200.
I do see the HD rear springs (8 leaf) with 7x17.5 tires which would raise the GVW to 5000 pounds, but those 17.5 rims are 6-lug p/n 3724684, the 17.5 8-lug rims are p/n 3724683.
The difference in GVW between the 3200HD and the 3600 standard is only 200 pounds (5000 vs 5200).
The 3200 cost $1,986.00 + 125.50 (7x17.5 tires) = $2,111.50.
The 3600 cost $2,132.00 (with Std 17.5 tires).
Why would anyone buy a HD 1/2 ton when you could get the standard 3/4 ton for $20 more?
I still believe your axles were installed outside the factory.
Mike B