Silvia roadholding problem

[smoker]

Hello, After getting my engine running better i'm now looking at improving the suspension. My car seems very twitchy on the back end when pulling out to overtake... feels like the change of road camber unsettles the back end making the rear wheels hop about which don't inspire much confidence.
I was thinking of fitting some uprated rear shocks and changing the anti-roll bar bushes but would appreciate some thoughts or any other recomendations before laying out my hard earned.