Leaf spring Q

[Green4.0]

I was looking on one of the Ford parts sites for new leaf springs for my 98 S/C 4x4.
I noticed they listed one for 93 through 98, and another for 98 through 2001.
Does anyone know what the difference is? I'm thinking one is an upgrade over the older ones or something maybe?
I'd like to get the best possible spring I can, but don't want one that's gonna be real stiff.
What springs from what will fit my truck as bolt-ons?

 

[mwtkinsw]

Explorer Rear Leaf Spring Assembly's

I located a set of 96 ford Explorer 4x4 four door, rear leaf springs, I know you need to get some #8 bolts to replace the existing locater bolts thru the leaf springs and flip them, to match the ranger, some people have suggested,
inter lacing ranger and explorer leafs, that's too much work for me, I plan on
swapping the bolts, maybe new neoprene bushingings at each end then install, if that is not enough, I will put in the block,in the front I will crank the TB's 2-2.5". I'm also going to use the stock explorer shocks, since they are new and the front shock extension bolt's, too keep from the shocks topping out and snapping off the end of the shock(http://www.totalperformanceonline.com/) and install 295.70rX16's.