Chorn,
A force applied through an arm is Torque. In flight the rudder would work about the Centre of Gravity. On the ground it would be a little more complicated to measure, as the anti-rotational force of the gear and the C of G would all effect the resultent required force.
Thrust IS a force, and the Rudder needs to produce a force in order to counteract it, but you are right in as far as, seeing as they would work through different lenght arms, they could be different values and produce the same equal and opposite Torque.