TT - greetings from Canada, Eh !
I'm envious of you - Toyota has not offered diesel trucks (and never cars, in my liftetime) here in a long time.
A couple of questions, if I may:
What is the factory tow rating on your '79 with this diesel ?
What transmission do you have ?
What is your typical mileage (mpg or L/100 km) ?
Is it NZ taxes that cause most/all of the price difference between your petrol and diesel ?
Our gas is not cheap here, but you are a good 30% over Canadian prices. Toyota builds a solid truck, but with that gas 4.2, I can see why it didn't sell in NZ, that would be very hard on the wallet.
Good example of expensive fuel driving diesel use up.
Rgds, D.