is it a shaking at just 60MPH? is it RPM related? what is the condition of your tires and chassis components? mileage?
1968 mustang coupe 357W: SpeedPro lower, XE282, Trickflow 185cc, Weiand, 650 Holley, gasket portmatch, Hooker Headers, Full MSD, C6, Built 9"
2001 V6: KYB adjustables, H&R springs, Cosmetics, CAI, X-Pipe, Full Exhaust, T5