Question for those of you with a digital CHT gauge Options

[era vulgaris]

For those of you who have a digital head temp gauge, what's your #3 cylinder temp after a good distance of highway running? Say like after 20 minutes between 3K5 and 4K RPM in 5th gear, or in the 70-80mph range?

Part of the reason I got my car with a 2270 for a proverbial song was because the PO was having serious issues with the engine running hot and I think he was a bit fed up with the car. I've spent a crap ton of time tuning the shit out of the carbs and engine, and also replacing a few sketch-ball parts he had on there. I can now run EZ-PZ in the 310-320F range on #3 all day long off the highway, up to 60 or 65mph.
But once I get on the highway and get above 70mph, my temps start climbing up into the 370's and even higher if it's an uphill grade.
I know it's a much greater load on the engine to push through the air at that speed, but the difference in temps seems abnormal. Or is it?

I'm wondering if the 916 bumper on my car might have something to do with it. Is it possible that the lower "splitter" part of the bumper is acting like an air dam, preventing cool air from getting under the car, and causing the temps to go up at higher speed?

Any insight is much appreciated! (IMG:style_emoticons/default/beerchug.gif)