Thanks for the input.
The biggest problem with running a diesel motor is that all diesels in NZ attract RUCs, Road User Charges, a tax graduated on the size/weight of the vehicle, which are charged per kilometre travelled, and payable in advance.
More bureaucratic bull#@!t to contend with!
My odometer is graduated in mph, and the RUCs are payable in kilometres...just imagine trying to explain to your average plod the disparity between the odometer reading and the RUC sticker in the window!

Mike, donor vehicles down here aren't out there in great numbers; the most common vehicles on our roads come from the land of the rising sun, and any second-hand American iron attracts a premium...which is why we imported the Chev chassis/motor/box initially...it was the cheapest option.
But the trouble with importing is that there's no come-back when/if the deal goes sour, as it has in this case; the 454 we imported as a good runner isn't, and you can't punch someone's head if they're 5000 miles away.
(Talk to the Lamin8r about this! He too got done.)
That was a big factor in opting for the crate 400; they're imported by by a Kiwi in Matamata, a five hour drive away...I know where he lives if it turns to custard.

But please keep coming with ideas and opinions.
(I guess that partly I'm trying to validate my own decisions!)