outboarding the coils is a great way to go if u are willing to put in the effort. it requires alot of work and a ton of space. u need custom width axles to fit them. u need to french the frame rails to fit them as well. if u are willing to cut the tub like vengeance, its the simpliest way to go with excellent results. u can run long coilovers as well.
the rig u are referring to is not a synergy/poly 8" stretch "kit". is has major work and plenty of additional fabrication.