So your going to take off a shackle lift and replace it with a SOA conversion? Just how long are your shackles?!? The SOA should net you about 6"+ of lift, And takes a lot of work/time/$$ to do correctly.
The return to center has to do with your caster (or is it camber?) and must be engineered into the lift, or corrected with shims (to a degree (pun intended
)
IMO, a dual stabilizer is not a solution for a problem, it just covers up the problem for a while. IF your suspension and steering is correctly engineered and build, you will not need the stabilizer.
Please read up all you can on suspension design, how a steering system works, and alignment specs so you can do the job once (more) and do it right.
I'm assuming by your location that you are planning to make a mud buggy? Give us an idea of your plans for it. Tire size is a biggy in terms of lift and usage.
post up some pics of your ride as is, so we can see what your working with, and give some good advice in getting your ride working great! Lots of smart guys here to help ya!