I just noticed this about the temperature guage on a '70 SS. The lowest mark is 100 degrees, the middle mark is 210 and the high mark is 250. There are 3 marks between 100 and 210, which would indicate about 27.5 degrees between each mark (the middle mark between 100 and 210 would be 155).
There's only 40 degrees between the middle mark of 210 and the high mark of 250, or 10 degrees per mark.
Besides the fact that these guages are hard to read anyway, the actual temperature seems rather suspect. Or to state it another way, a deviation below the mid-point is less significant that above. Or yet another way, the change in temperature according to the needle is not linear.