Temps I see when on road are about 200 - 220 degrees F for plug, seen it get to about 240 degrees.
My data logging is still a bit noddy, I couldn't say how accurate the actual figures are but it's useful as a comparison tool.
Not messed with head, ignition timing and temps much yet, but it's on my list to do.
Here's a graph of some sprint runs.

Edit: changed from degrees c to f, duh.