I am restoring a 73 Cuda, really long term project. What was the reason for having different part# leaf springs (left and right). Shouldn't they be identical, unless they were compensating for something.
Your 440 6bbl and Hemi cars definitely had different numbers of leaf springs between the left and right to help prevent axle hop. XHD Mopar leaf springs (made in Mexico!) is what I have on my 70 Challenger and 71 Barracuda.
Some of the leaf springs for the 225/318/383-2bbl were the same part number left to right.
On the torsion bars, if you lay them side by side on a level surface you will see an ever so slight difference in twist between the two bars. I think once you get up to the really big aftermarket bars, the bars are the same left to right.