This is a list of the available torsion bars for the Challenger. Which bar you got depended on engine and if the car came with heavy duty suspension or not.
All E-body cars came with a 41 inch long bar (same as B-Body).
Diameter of the bar is listed in inches.
225 six =0.86
318 1970 = 0.88
1971- 1974 = 0.86
HD 1970-1974 = 0.90
340 1970-71 = 0.90
1972-1973 = 0.86
HD 1970 - 1973 = 0.90
360 1974 = 0.86
HD 1974 = 0.90
383-2bbl 1970-1971 = 0.86
HD 1970-1971 = 0.90
383-4bbl = 0.90
440 1970 = 0.92
1971 = 0.90
426 Hemi 1970-1971 = 0.92