140 Litre Petrol tank is still a good size and if getting around the 15 Litres I would rather the V8 Petrol than my 3L diesel when travelling.
Not sure I would add long range tank, I expect with similar coin you could add a rear bar with wheel carrier and twin jerry holder.
The margin between Petrol and Diesel at the bowser fluctuates and often balance out however the luxury and the power would be pretty awesome to have with the V8. When I bought my GU 2 years ago there was still around $30k difference between the Y61 and Y62 so went with the GU.
The Y62 will be a big possibility for my next vehicle, if they are still around, and the prices continue to drop.
Agree also with the crap with EGR, DPF etc on many diesels maybe petrol is the way forward. Dunno.