Leaf springs

[Gator]

For my 71 340 duster with a 9" Ford rear end---Ok well this leaf spring deal is becoming a nightmare. My springs came yesterday and they sent me the wrong ones. The front bushing diameter is 3 1/2" Oblong where the original that are on my car are 1 1/4" and the rear bushing on the new srping is close to 1 3/4" oval where my original is around 1 1/4". Looking at other springs at different sites both ends look to be the same and I also noticed that there are left and right leaf springs which are different to each other and then some sights mention both left and right springs that are the same. I noticed that the left spring has the leafs offset and more towards the front of the spring and the right side the majority of the leafs are in the center of the spring. Whats the purpose of the left spring being off center? My current spring set up is both springs are the same with 5 leafs on each spring with the thickest part of the springs in the center. Also was mentioned that the left spring has 7 leafs were the right spring has 6 leafs. Whats up with this? Sure could use some professional input...