Well, I guess it depends on where you're sourcing the parts from, whether the axle you get has a matching gear ratio, and how much you're paying for everything else needed to mount it under your truck (new steering linkage, bushings/links/brackets, possible driveshaft modification, etc.).
If you do SAS it, don't use anything less than a D44 axle. This way you won't be going backwards in strength.
Being you already have coils under your truck, it would also be easier to keep it as a coil setup than to switch everything out to leafs.
Used TTB lifts often can be had for under $150 if you look around some, new ones start around $450 and go up from there.