Mark brings up good questions. Engine and oil temps will be affected by all of the things he is asking.
I am going to assume that you are using an oil temp gauge to gauge the temperature of your engine.
Obviously, this is not an accurate measure. You would likely need something like an infrared laser thermometer to tell the actual engine temperatures.
Tecnicalities aside; Remember that these are air cooled engines. Air must flow across the engine to help cool it. To aid engine cooling, things like oil coolers, fans, etc... are used.
With that said, "What is a "normal" operating temperature for the engine?" I don't really know.
For the purposes of engine maintenance, warm up the engine (at idle) for 10 - 15 minutes. Take a reading of your oil temperature. That should give you a "normal operating temperature".
Under racing conditions, things change quickly! Oil temps can shoot upwards of 300 degrees, depending on how hard you are pushing the car and how much cooling the engine is getting.
I know that doesn't exactly answer your question; But best answer I have for you.
Steve