the stock valve springs can handle the autotech 262s but not if you beat on it, its a good idea to upgrade them. while your in there dont forget about lightweight lifters and retainers too. as for valves, you dont buy the seats they are cut by a machine shop. anytime you change valves you need to have the head matched to the valves, and shave a couple thou off to clean up the surface. you will need a overhead valve spring compressor tool to get the springs and valves out, and the valve keepers can be a real pita. also dont forget new valve seals and guides. have fun.