My 2005 uses the variable pitch of the turbo vanes to work like an exhaust brake, but it is not as effective as newer setups. My cruise control can be enabled over 25 mph. The most weight I have hauled without additional brakes has been 15K lbs GCW - The engine controlled my braking and I never felt out of control or taxed. With trailer brakes, I have not hauled more than 20K lbs GCW, but that was easy when you have four additional brakes at your command and can tap the pedal to keep things in check.
Ford also has something called Hill Descent Control, but I do not know if it is a feature that only works in 4x4 application or also in 4x2 since it came out only a few years ago.