Same rear axle and brakes between a single rear wheel and dually regardless of 3/4ton or 1ton.
That truck does NOT have airbags.
That is stupid to be doing that and puts everyone around him in harms way.
Flat stupid!
For those that asked yes the truck and trailer are both over weight, everything about it is illegal.
That's got to be near (or over) double the OE tow rating, and that's assuming he meant 2500HD and not actually plain old 2500. Just plain dumb.