Curious. I've had a CHT gauge for years, mounted where the radio is supposed to be. It's made by VDO, and the thermocouple has a washer that fits underneath one of the sparkplugs. I use plug #1 since I was told that #1 typically runs hottest. At cruising, I see about 225F typically. Really hard runs uphill will push it to 300F, coasting downhill can drop it to 175F or so. My oil temps are typically 180F, but it will get to 195F on hot days (street driving).
Doug Clauder
1975 911S
http://members.rennlist.org/dougcl