4-link
They pretty much already have a 4-link. Most folks at some point (as their car gets much faster) put on adjustable uppers, boxed lowers, maybe airbags, pinion snubber.... I also think they have a control arm re-location bracket for either the uppers or lowers... not sure which..... that will change the instant center...... but for the most part..... the factory 4-link works pretty good IMHO.
HTH