Also depends where the pickup is located. Whether the temperature is measured before or after the cooler. Torque converter outlet will read quite a bit higher than the pan, especially if the converter has been operating unlocked for a period of time. With my old 4spd 47RE which only had lockup in 3rd and 4th, I used to see temps as high as 270 with the converter unlocked. It went back down quickly after the converter locked up again. Synthetic fluid handled it OK.
Normal operating temperature with the converter locked was 150 to 170 depending on ambient temperature. The 68RFE in my present truck is about the same.