When I had Sunbelt build my racing NA 3L L6 the dyno testing showed the engine made the most horsepower and torque with the coolant temps at 200 to 205 degrees and the oil temps at 220 to 230 degrees. YMMV but what they saw on my engine was similar to what they saw on the racing BMW M50 engines they built for World Challenge Touring.
I ran a 190 degree thermostat, a 32 psi radiator cap, and a oil/coolant heat exchanger to keep both liquids near the temps lsited above.