I have the Air/Fuel ratio gauge with an O2 sensor, as well. I "know" this gauge since i had it in my totalled 1200. The EGT seems to peek at 1300-1400 deg on cool nights. At the same time the A/F gauge reads off the scale lean. During the day or on warmer nights, like to night, the EGT goes up to 1200deg or so and the a/f is in the Green or just slightly rich. If I floor it, as the rpm's climb, things start leaning out and the EGT temps climb.
All these temps are when I'm crusing on the freeway, at about 3000-4000 rpm.
I'm still fiddling around with the SU's. I havn't quite figured them out yet, but i guess I'm getting close.

An oxygen sensor kit is the easiest for rich, normal, lean indication but only works with unleaded gas. They simply read off rich, lean, or on.

The absolute temperature varies by engine, where the EGT sensors are placed and other factors.

On airplane engines, EGT is used by adjusting the mixture control to get the highest temperature, which is the optimum burning air-fuel ratio. Then the pilot either turns it richer, until say there is a 100 degree temperature drop, or some pilots run them leaner. The temperature drops each way off the peak (rich or lean). Lean of peak gives best fuel economy, but could burn the pistons, valves, etc if not careful. Rich of peak is safest setting for the engine. Slightly rich gives best power. Richer still cools the engine, especially under turbo boost.

For emissions controls and fuel economy, most auto engines (carb or fuel injected) run just slightly lean of peak, except at full throttle, when they run (hopefully) at the max-power rich setting.

I put an EGT gauge in my car just for 'shits and giggles'. It's a dual egt, one probe on #2 primary and one on the #4. I figure i can monitor both carbs.
I've seen these installed in a few cars in magazines and the like, but no one ever says what the temps should be or NOT be. A warning label with my newly JetHot coated headers says not to get above 1300deg or i could affect the appearance . Which means there is some aluminum used in the coating that starts to melt at that temp.
I'm interested to know what is normal, lean or rich in any car.
Thanks
angelo