Outside temp display
 

When I got my 87 300D the temp display was no good, I had a parts car (95) so I swapped in the display. It works but is always off by 10 degrees. My 87 was in Fahrenheit but the one I replaced it with is in Celsius (my preference). Everything I have read says they are interchangeable but I’m not so sure. Is the probe outside the same or is that the source of my problem? Or could the display simply be bad? Anyone have this issue?

In 95, the computer had an algorithm to be more accurate with road conditions etc.
So yours is likely calibrated for that offset.