I believe that most readily available thermo couples ( the EGT Sensor ) are similar in design and shape

Welding a "bung" into the down pipe post turbo is simple to do. As mentioned above it gives a 300*F lower reading. The benefit is the same. You have a threshold for safety. It is said that you can be in the red about 45-60 seconds before damage occurs. So post turbo, 900-1000*F for a minute is fine if you MUST push the limits in an emergency situation.

There are also benefits to removing the turbo, manifold, EGR, etc and making sure its all clean. At that point you might as well install the TC 'pre turbo'.

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85 300D 3 pedal. Current project.
83 300TD (need rear wiper assembly dead or alive)
84 300SD Daily driver
85 300TD almost 400k miles and driven daily.
98 E300D *sold
86 300SDL *sold and made flawless 10 hour journey to new home.