If the problem goes away when you restart the car, it’s reasonable to assume that there’s something electronic that’s responding to the rest, or there’s something like a crank angle sensor that is getting hot, delivering bad information to the computer and then working fine again once it’s cooled down.

Have you had the vehicle scanned for fault codes? This should probably be your next step rather than simply changing more components that don’t turn out to be the problem. Meantime, don’t rule out things like the spark-plug leads or even a failing fuel pump. How about something from left-field. I’ve personally seen a dirty fuel filter allow a car to run perfectly for the first 10 kilometres, until the gunk built up on the filter element and stopped the fuel flow. Switching the engine off and then back on again, allowed all the rubbish to fall away from the element and the car would be perfect for another 10km. Until it wasn’t.

Yes, like the vast majority of dual-cab utes sold in Australia, the Holden Rodeo was indeed built in Thailand, at the Isuzu plant (the Rodeo was an Isuzu D-Max under the skin apart from the petrol V6 version which used a Holden-made engine). But diesel Rodeos used the Isuzu 4JJ1 four-cylinder diesel which used a timing chain rather than a rubber toothed timing belt. As such, the chain should be good for the life of the engine.

If the engine were reconditioned by a reputable engine reconditioning company and they gave you a guarantee with it you can be confident that it will last a long time. How long is impossible to say. There would be little difference between the exchange reconditioned engine and the one done by your mechanic. Either way you should check on what they are going to do the engine in the reconditioning process, so you can be confident that it is done professionally and properly.