I agree, I will use synthetic with the new diesel engine. Keep in mind, though that those figures are from right under the sparkplug - the very hottest part of the engine, and one that doesn't get oil. You could probably put the sensor under a head bolt and lose thirty degrees instantly.
But it confirmed what I had been told... these big singles run HOT. I suspect a lot of engine parts failures have to do with a combination of heat, poor metallurgy, and particles in the oil.. put them together and its a destructive mix. Using synthetics offers you a greater "margin of error"... but my advice is to use synthetic oil, change it every few hundred miles, and keep a close eye on tolerances.
Yes to iron engine and stock gasket. My engine's fairly beat, though; this standard engine was badly coked when I got it, and the piston wear was nearing the max allowed (65 thousands).
The new diesel is a whole new field of discovery... and all without any good manual...