Cliff, Customs and Quarantine like any imports to be squeaky clean. Usually this means a steam clean at point of departure and again at port of entry. That said, one lot of parts I brought over were recommended to be sandblasted first! New Zealand does not have the same problems with spiders and snakes, but Quarantine thinks that Apple Fireblight grows on trucks.
You will also need an import permit application from
DOTARS which will require as many identifiying numbers as possible. Then find a shipper who will ship a virtually empty 20' container for less than $1800 and you're on your way!
As Keith said, unless these trucks have some sentimental value, it might be easier (certainly cheaper) to find one here.