if you want the car to ride and handle like a new 1968 mustang, then you just need to replace the bushings and springs with new ones, along with shocks, and your done. if onthe other hand you mean you want your car to handle and ride like a 2005 stang, you have your work cut out for you, and you need a bunch of money. the easist way would be to contact air ride suspensions and get their complete ari ride suspension kit for your stang(about $6000 for the complete kit) and install that. your biggest ride and handling improvement is going to come from redesigning the rear suspension for better suspension compliance, and to take advantage of modern radial tires.