don't replace the guides. rebuild them with bronze walls that way you will be set up for unleaded gas. the seats if they are not beat out then don't replace them either they don't need it. check around on the valves you mite be able to do better. you did not give a price break down.
as for the checking around. i need an exhaust kit for my 72 truck one place wanted 219.99 the next was 154.99 same part number same manufacture.
