What Brian said.

We learnt quite a bit when we stockpiled the 5.0l wheezers in Aus for the AU Falcon's after the engine finished production in the states in 98 (I think), and we were still putting them in cars till 2002. A lot of them got rust (or other damage to seals etc.).
As a result of things like excessive oil consumption from rust on cylinder walls in some of the earlier engines that were put in storage, they had to do a full engine inspection (and possibly rebuild!) prior to install in the AU MkIII's.

Safe to say, we didn't want to repeat that mistake
The 7.3l (and 4.2l) was built to order tho by Navistar Brazil.