Towing Mods: how hot can we safely get a D24T?

[casioqv]

In one month I'm towing a 3,000lb Catalina 22 sailboat over the infamous "grapevine" mountain pass in southern california, with a peak altitude of 4,160 ft. My goal is to prepare my 1984 760 diesel in advance such that my engine survives this difficult task. My brakes and suspension are already heavily upgraded, so I'm *only* worried about engine cooling issues here. The boat trailer also has excellent and brand new brakes. The car is also factory rated for towing this weight.

Anchored off Santa Cruz Island this January, after towing to the launch ramp with a 740 Turbo:


Goals
-calculate EXACTLY how hot she can run, and monitor closely such that I pull over before damage occurs
-modify the car to maximize the margin of safety
-plan a safe driving strategy
-have an awesome trip sailing with my dad in the California Delta

Engineering starting premise
The engine will be fine as long as the coolant remains in the liquid state. Therefore, I will estimate as accurately as possible the true boiling point, and not allow the engine to get within 5 degrees Celsius of this value.

Please no comments about how I'm "over-thinking this." I'm an engineer, and I enjoy solving problems this way.