[reaperducer]

if US Postal Service was willing to buy foreign vehicles,

It's not. Offshoring critical infrastructure is always a bad idea.

they'd have to deal with EPA and NHTSA rules

Possibly not. They don't even have license plates, as the Postal Service outranks state governments.

[ggreer]

The NGDV's gross vehicle weight rating is 8,501lbs so that it is classified by the EPA as a heavy-duty truck. If the rating were a pound less, it would be classified as a light-duty truck and have much stricter emissions standards.