M923 5-ton 6x6 truck, wildlands fire truck conversion.

The M923 was the last in the line of a series of 5 ton US military 6x6 trucks.  A 6x6 remains in service, but it's a cab over.  

Featuring a Cummins diesel engine, a 5 speed automatic transmission and single, rather than dual, wheels the truck was, and indeed is, quite modern.  Built by AM General, with production commencing in 1982, over 44,000 of them were produced, and they remain in service around the globe.

Not surprisingly, like prior 6x6 trucks, they've gone into civilian use in various roles, including as wild lands fire trucks, such as this example.