Poked a hole in the radiator replacing the alternator...
LUCKY! ... 
Its time for a new radiator anyhow...
Upon draining the old unit, it appears that I have been using diesel for coolant for a long time. I mean 2/3 of what came out was brown, low viscosity liquid that smells of paint. The green coolant was clearly visible, layered below the fuel (?)
Any lesser engine would have died long ago, I just towed a trailer from Perth to Adelaide. There was barely any indication that this was happening. But there were hints:
Splash marks in engine bay where coolant had shot out around overflow bottle. I passed that off as an overheat while beach bashing in Perth...
Oil weeping out of turbo air intake for a while, turbo boost seemed lower, but I passed that off as engine wear and tear.
Engine dripping a little oil, I just took it to be a poor seal on the rocker when I replaced the ORPS. No big dramas, no noticeable change in oil level between 5,000k servicing.
So here I am. Plan is to drain fuel tank and look for contamination. Ditto for engine oil.
But here is the rub. I love the truck, it has seen me on-my-way from Cairns to Perth to Adelaide, crazy bush bashing adventures every step of the way 
. I've got a new alternator, new radiator and would love to keep her going.
What are the chances that the standard injectors/seals/sleeves/gaskets swap will fix it?
Is that my first port of call? She has had all bar the last recall done on her and 290k on the clock... I don't have any time or money to waste..
Also, a good mechanic in Adelaide to perform the top end rebuild?
Cheers from a Noob. I have saved the Jack from an untimely death 3 times, thanks to this forum, but this one is a bit above me.