that patrols engine was a reliable old donk compared to the 3.0, not in the race comared to the td 4.2 but you are high in the km range already, start saving straight away for a rebuild in 3 years ...possibly.
How much is a well looked after early model td4.2 the non turbo model (it can be added later)...it's the toughest engine ever sold in a vehicle, the only reason they die before 1m km is owner abuse ie overheating, poor oils, lack of servicing etc.
If it where me and I luv the 4.2 engine like no other I have ever known, I would opt for the petrol and put it on gas, will blow the diesel away in the sand and everywhere else. Forever save money on fuel and the purchase price.
Sorry I don't know the Hilux.
cheers fnq