Add A Leaf?

Three cars I've owned had extra leaves added. Someone had added 1 to a 68 Road Runner. Seeing that it matched exactly one of the others I concluded it came from another b body.
So I have done it to 2 of my a bodies, I just pulled a set off a parts car and tried the different lengths and used the one I liked best. I put about 30000 miles on a Swinger after that, and I have around 15000 miles the Road Runner.
I added one on my current Duster 2 years ago.about 6,000 or more on that one so far. I'm completly satisfied with the results, and the ride only stiffened slightly.
!!!My one comment is I have also added swaybars to the front. with a stiffer rear spring the roll characteristic will change and cornering might feel a bit squirelly.!!!