As for engineers cert. They're easy to obtain, The hard part is forking out the $400 odd for a few pieces of paper.
To be completly honest/nieve I highly doubt a cuntstable is going to make you pop open the bonnet on a 4WD, especially a Zook, unless he's an enthusiast too. In my last car, A cop pulled me over because he saw on his computer that it was engineered, He only wanted to check out what I had done, only because he knew how rare that model car is and his missus had one and he liked what I had done to it.
But of course for insurance or peace of mind purposes, It is a wise idea.