What do I NEED to achieve the perfect level?

So as many taco owners I've decided to go with Bilstein 5100s on all 4 corners now I just don't know if I should replace my factory springs from 2011 with 114k on them or just keep them?I'm really looking for a smoother ride so don't know how much those springs could effect the ride but thinking if maybe I was to get a spring that lifted the truck its self and not rely on the 5100 the ride would be better? anyway any spring suggestions? thinking of mainly leveling it right now and MAYBE just maybe down the road ill do an add a leaf

 

Buy new take off OEM suspension and 5100s set to .75 up front. Replace leafs, front and rear shocks and coils.

$500