B and E bodies both use 41 inch bars. The thicker the bar the higher the spring rate. The higher the spring rate the better the car will corner but the stiffer the ride.
It is foolish to mess around with suspension rates unless you have a fair idea about what you are doing.
Some people (americans in particular) prefer to increase the sway bar size and keep the torsion bars and rear springs near the original spring rate so that the ride does not feel too harsh.
In the rest of the world it is normal practice to increase both the sway bar diameter and the main spring rates.
You also need to keep the front spring rates in line with the rear rates. The factory did not do this very well but you can.
If you just increase the front spring rate by adding a sway bar and stiffer torsion bars without beefing up the rear springs and adding a rear sway bar then the result will be massive understeer on your car.
Read this very good book on the subject;
Super Street Mopar