coolant temps

[steve k.]

I have a 1981 C30 with a 350 instead of it's original 454. Most of the time the temp gauge sits at 1/4 and occasionally moves to 1/2. The truck is only used for towing my race car and I am about to take a long trip from San Francisco to Seattle. Climbing 10000 feet in what could be 100 degree heat. A couple questions I have are:

1. what temperatures are at 1/4, 1/2, 3/4, and red on the gauge?
2. what is normal operating temp?
3. can the stock fan be replaced with another to draw more air without going to electric fan.
4. does "Tow Cool", "water wetter" or any other additives to the coolant work for keeping the temps down
5. what can I do to keep the temps down on the trip?

Thanks a lot forall the help,
steve k.