G'day Simon, I have an ex Telstra ute with a Rossco's canopy, set up for long term & remote area touring. It is a 4.2 though, so not directly relatable to your question about fuel consumption. That said my fuel consumption (towing a Tvan) is not that different to what others have said they get from their 3 litre wagons, which surprises me. I have recorded our fuel consumption on a phone app over the past three years as we travel around Australia (see Blog link at bottom of post). Bear in mind a few factors. The 'Telstra' body is wider than the cab. I have a canopy roof full of solar panels, plus one on the cab roof. We are relatively heavy & with all tanks full & supplies restocked travel at just below our extended GVM of 3900kgs (including tow ball weight of the Tvan -105kg). In addition the Tvan loaded comes in at between 1100kg & 1200kg, so a total rolling weight of around 5.0 to 5.1 tonnes. And yet our average fuel consumption is in the high 15's (litres per 100kms). Lowest has been just under 13 & highest just over 20.

I suspect that the big difference between how I achieve that sort of consumption compared to the lighter, non towing 3 litre vehicles is speed. We enjoy taking things slowly, we have no need to rush & on sealed roads would probably average only 80kph or a bit less, when towing (which is around 80% of the time), & between 80-100kph when not towing. I rarely rev the motor above 3000rpm, & tend to drive more to the EGT gauge with it averaging around 300deg.C.

As to the suitability to set up as a tourer - I think they make a great deal of sense. The canopies are solid & well made & offer a lot of room to set up your custom interior. They (or at least my one) come already fitted with dual tanks for longer range, dual spares, & a Warn winch, a bullbar & a 2" lift. All essentials for the sort of travelling I wanted to do. There is the downside of compromised rear vision, but Nissan mirror extenders on both side are not expensive ( if the vehicle you have doesn't have them) in addition to fitting a rear vision camera (as opposed to a reversing camera) make it good.

I am not sure if the 3 litre models Telstra used had either coil rear or leaf rear or utilised both on different vehicles. You need the leaf sprung version for it's higher weight carrying capacity. Even with my factory standard
GVM of 3400kg, it was easy to exceed this. Ours came in at 300kg over GVM, & whilst I could reduce this a bit it would have been impossible to lose 300kg without ripping everything out & starting again. Hence the (expensive) GVM upgrade. We do however have the ability to stay off grid for up to 6 weeks. If starting over & staying more simple/basic & could remain under the factory 3400kg if careful, but then I wouldn't have what we have which allows us to do what we do in the way we like doing it! Check out our set up at http://cuppa500.com/Blog/modifications/

There are two makes of canopy that Telstra have used as far as I know, the Rosscos that I have, & the Obeico. There are a few minor differences between them (eg how the driver side canopy door opens & the design of the swing down spares carriers), but basically they are very similar. If I were looking now, the choice of canopy would be secondary to the vehicle condition.

The two things I would change were anyone to give me a magic wand for christmas would be to somehow make the cab more spacious, & to have more comfortable seats. (Oh for adjustable lumbar support). But overall I love my Patrol & it has never failed to impress me with it's off road ability, even with the weight & Tvan behind. On every occasion we have been faced with an off road driving situation where if there had been a chicken track I'd have taken it, but had no choice other than to push on, the Patrol has not let us down, leaving me with the sense that the car is far more capable than I am .... which is just the way I like it! The 4.2 is a great motor off road. I don't know about the 3.0s, especially if towing. I'm a bit out of touch with prices, but I'd suggest that if you can find an ex Telstra 4.2 TDi with less than 300,00km on it for similar money to what you are looking at spending on a 3.0, at least include it in the mix of possibilities. It won't be as quick away from the lights, but it'll be a far better tourer if off road & remote are to be part of the dream.