Early A leaf Spring Replacement Help

I am swapping out my rear end to an 8,3/4 om my 64 Dodge Dart & was planning on using the original springs because it was a 273 V8 model, and just upgrading to poly bushings! Then I decided to $ out new leafs but could only find 65 & up!


My 1st question is what is the difference if any & what is interchangeable43-414.jpg ??
example:Mopar A&B Body Performance Leaf Springs | Mopar Leaf Springs