So, I slept over my tinkering ideas. And had a closer look at the car. Hence, a change of plans. A) I need a new oil cooler, the old one is leaking at the thermostat and one crimped in hose. And the connectors are impossible to remove from the cooler, so a new one with thermostat and fittings is in order, now, not end of this year.
B) the sump pan is leaking at the front left corner, no idea why. If it is the sump pan, assuming the engine block is good, I might a new one as well. Not now, but later this year.
So no fancy mods, the necessary stuff first. Expensive enough, if you want good quality. Only mod, becaus it is easy to do, are better valve springs.