1985 745t

Given that my heater valve is failing, pressure cap is slightly split, and radiator has a pin hole leak I've decided its probably time for a cooling overhaul. However, I'm having trouble with a couple of the parts that are available with different temperature settings, and am hoping someone can point me in the right direction (the FAQ doesn't really supply technical or specific information on teh subject, I looked).

Thermostat
Everyone says 92 is for cold climates, 87 is for hot ones. Why? I primarily drive my brick from Vermont down to Philadlphia, so I would assume I should use the 92. However, it seems to me that keeping the engine a little cooler and farther from higher temps is a prudent move... sure, neither temp is very hot, but is there a reason I wouldn't want to use an 87 and protect myself against a really hot summer on a hill?

Nissens Alum. 2-Row Radiator
Does this radiator come with the newer screw-in aux. fan actuator design? I haven't been able to find any images and don't want to order the radiator only to find myself having to order and wait for the actuator and hose.

Aux Fan Actuator
The parts listings I've seen list only one temperature range for the in-hose sensor, regardless of whether its threaded or push-in. However, the threaded sensor that these listings recommend for in-radiator models has three temperature ranges:

823 959 481F (92-87C)
175 959 481 (94-90C)
251 959 481 (102-97C)

If I remember correctly the volvo sensor triggers at around 204f or something prcariously close to boiling. It would be nice to get a lower temperture sensor as a guard against overheating, but how low to go? 102C strikes me as a little stupid...

Thanks in advance for any help, just kind of stumped on the exact reason to go with different ranges and temperatures.

-rt