Why? How do you know the factory didn't do the same thing, how much cross weight is incurred by doing that, what effects that would have on handling, and that the torsions were equally loaded in the first place?
I don't know - I said it did not "sound like a good plan". When I say that, I mean that I respectfully suggest that you check into it. But the "it's your nickel" part was also my attempt at respectfully acknowledging that it is up to you. IOW - what are the alignment specs for the car that came with these springs (factory 340 that is). If they show what you are doing to be correct then that settles it I would say. As to the SS springs - I'd suggest reading the old Direct Connect chassis manual for that - I actually have one but not with me at work. I don't know where else you'd get specs on that except to ask someone who knows how to set them up. But those were designed for drag racing only. If you like the look (I had them on my Duster once myself) fine, but I would not expect good road manners from them.