5100 upgrade

hey guys,
I'm looking at redoing my suspension in the next few weeks and just wanted to get some advice.
Currently I have a pro crap lift on, when I got it installed at 4 wheel parts 4 years ago they left the add a leaf on from a old spacer lift and then added the block spacer that was part of the pro crap lift. I'm looking at doing 5100's and the 112-620 Eibach/Toytec front coil springs 620lb spring rate. my question is do I pull the old add a leaf and block and do a new add a leaf or just leave it all. I'm looking at getting a smoother ride from what the pro crap has. I'm going to add airbags as well at the same time that I acquired from a friend