Spring rate is spring rate, it is independent of vehicle. In a coil spring it would be pounds per inch of compression, a torsion bar would be pounds per degree of deflection. So a B body torsion bar and an A body torsion bar with the same spring rate deflect the same.

What you are thinking of is wheel rate. Wheel rate is the rate of deflection at the wheel. Being that our torsion bar suspensions use the inner pivot point as the spring attaching point the ratio, regardless of arm length, is 1. In a coil over type suspension where the spring attached somewhere between the inner pivot and the outer pivot the ratio is less and is a function of those points and the angle of the spring.

https://www.hypercoils.com/spring-rate-calculator/