My Toyota manual, diesel 4Runner has oil in the radiator, my mechanic has done everything, new head gasket, machined the head for warp, pressure tested the engine block, but the engine oil is still leaking into the radiator, he reckons the engine block has a crack but the engine power when I drive it is very powerful, no sound or lack of power, his got the vehicle again to re-check the engine block, my vehicle used to have air-con but the compressor was taken out a few years ago could this cause the problem

Is your vehicle equipped with a radiator mounted oil cooler or transmission cooler?
If it has either, it's possible that it is leaking and mixing with coolant.
That is usually how you find oil in the coolant rather than coolant in the oil.

I'm not sure however, there is an oil cooler system under the muffler manifold, it's the muffler manifold with 4 metal pipes that fit on the side of the engine, just a note; you know where the oil filter is fitted well a new gasket was fitted to that whole unit because there was a worn out gasket... if that makes any sense, my mechanic thinks that unit is faulty cause it looks worn, my vehicles has done some 300,000+km

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I'm not sure however, there is an oil cooler system under the muffler manifold, it's the muffler manifold with 4 metal pipes that fit on the side of the engine, just a note; you know where the oil filter is fitted well a new gasket was fitted to that whole unit because there was a worn out gasket... if that makes any sense, my mechanic thinks that unit is faulty cause it looks worn, my vehicles has done some 300,000+km

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Under a hot exhaust manifold is not a normal location for an oil cooler. Can you get a digital pic or three? That may lead to an external cooler unrelated to the radiator...
Exactly how did you determine that you have oil in the radiator?

OK, I thought there was an oil cooler where the oil filter fits?? (wrong), at first I saw an oil slick in the radiator and didn't take much notice until a week after when I checked the radiator to fill water I noticed that the slick turned to a thick oil sludge, I checked the oil stick and the level of the oil was halfway between the full and fill up marks, I topped the oil up and the radiator with water and went to see my mechanic, there is no oil sludge or water mixing with oil in the engine just normal engine oil. The vehicle is with my mechanic at the moment so I'll try and some pic's won't promise. By the way thank you very much for helping out a guy from Papua New Guinea (pacific) we are just above Australia

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OK, I thought there was an oil cooler where the oil filter fits?? (wrong),

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No, not wrong! That is likely where the oil cooler lines connect, but they run from there to an area where it is far cooler.
That is to say: from the oil filter adapter, the oil cooler lines will run forward to allow more effective cooling. Sometimes they plumb to an external cooler and sometimes they plumb to a radiator tank and the oil is cooled there. I'm thinking that the heat exchanger that is built into the radiator has failed and is allowing engine oil into the coolant, which would result in a fairly simple repair.
Let us know what your mechanic finds.
Papua New Guinea? I've been to Guadalcanal and sailed the Solomon. You're about 9,000 miles away from where I'm at right now!

CapitanRich, my mechanic fitted a new engine block and the problem has been fixed, he reckons that there may have been a very small crack inside the oil lining that cools the engine causing the oil to leak to the radiator by pressure build up. After fitting the engine block I have problems starting the engine in the morning I have to pump the accelerator then after about 4-5 pumps the engine starts up, this happens in the morning when I first start the vehicle but after that it seems to be okay.

Just so we're on the same page, all you're doing by "pumping" the accelerator is opening and closing a throttle valve.
Try holding open when trying to start cold. If this improves starting, then I suspect an over rich condition from a dripping injector overnight.