These are bolt on ready to go. The valve springs should be checked to very correct spring pressurea to match what ever cam your vehicle has. They are 2.02/1.60 valves, screw in studs and guide plates. They are early ones with no accessory bolt holes. They were redone by TPIS just before I bought them. Was going to use them on my Chevelle but have decided to go a different direction. $700 b/o