S13 and S14's do have different sway bar and are not interchangeable, I can't remember exactly what is different off my head. What is your ride height at now? And considering how much you are interested in suspension geometry, I would say it's worth the money even if it's for an experiment, because at the end you will have better suspension, if not at least resale value of the springs will remain. someone is always willing to buy swift springs off you.
Update when you do get knuckles(I'm going to assume you are getting drop knuckles to level out the LCA angle while lowering CoG)
edit: which swift springs are you looking at buying anyways?
http://swiftsprings.wpengine.com/pro...lover-springs/