Gents,
thank you all for your valid feedback and advice. Appreciate!
I finished my research and came for me to partly different results which I like to share (and later on prove or disprove in reality and share again, of course).
First of all I like to agree that the best oil temp is around 212F. However when the right water temperature comes into play the opinions here in the chat are in favor of a hotter temp towards 180F (or even hotter).
Now let me quote my engine builder who is doing high performance tuning of Cleveland and Windsor engines for the last 36 years successfully:
"I was told this many years ago (edit: colder engines produce more wear), but have never experienced it and I have been tuning our engine packages to 160f and colder for many years without any complaints from customers of excessive wear. Nor have I witnessed excessive wear when freshening one of our engine packages.
Car manufactures do run engines very hot these days compared to many years ago as it helps to burn every drop of fuel and it greatly helps with emissions. Our packages are not built around being emissions legal. They are built around making max power for a given fuel. If you try to run the engine hotter there will be more hot spots in the chambers and it will cause detonation resulting in engine damage.
Just going from 160F to 180F would probably cost you 10-15 hp and you'd be risking detonation.
If we lowered the compression ratio so as you could run the engine at 180F without the risk of detonation you'd probably loose another 10-15hp
So in total you could lose 20-30hp just from running the engine a little hotter.
I have seen far more damage created from running a high performance engine hot than compared to running it cooler.
On another note I find that once you get an engine hot it's much harder to cool it down compared to not letting it get hot in the first place."
I must add that driving conditions are severely different here in Germany than in the US. When you talk about 75-80mph on the interstate we talk 120mph cruising on the left lane of a three lane Autobahn. That's fairly average. If we go fast we are doing 150-200mph (of course with the right cars). If we go slow in that lane its still about 95-100mph. The strain on the engine is and will be a different ball game.
To keep my water (and finally oil) temp down I will apply an electrical pump (55g/m) and two SPAL fans with a controller by applying a high-performance mesh cooler and large oil pan. I hope the precautions are rightly set.
I will report back when its ready to run.