Softer ride with 18"

[Bowtieracing]

I have found my vettes ride little too harsh when driving on goglestone city streets. It makes everything rattle even at slow speeds. Is it just a trade off with 18" low profile tires or should try rubber bushings instead of polyurethane(energy) ? I have 480"lbs front springs and matching rear I dont think the are too much for low weight mid year cabriolet corvette. My shocks are non adjustable bilstains. Should i try adjustable konis with soft inpound ?