Instead of just heading to the local Kenworth dealer and picking out something in green, the US Govt spends years working with contractors to create a design specification to meet their trucking needs. Subsequently, they pay a builder to make the vehicle (per the previously defined requirements) which might change over the years as
If interweb sources can be believed, Oshkosh currently owns the contract to produce the FMTV (Family of Medium Tactical Vehicles), but back when this beast was built it was Stewart & Stevenson, a medium sized corporation out of Houston, TX. The LMTV (Light Medium Tactical Vehicle) version is very similar to a Steyr 12M18 and is powered by a 7.2 liter CAT C7 turbo-diesel inline-6 and rated at 2.5 ton capacity.
The M-1078 variant is the standard cargo version which offers an open bed out back for maximum hauling. For proper zombie apocalypse survival you probably want the M-1079 Van version, but the cargo version would work in a pinch. This one even comes with a passenger seat pre-soaked with back sweat.
See a cooler car to pickup the kids from school? email@example.com