I have used the search button but could not find the specific answer to my question, which is: What type of valve seals are recommended for a 1958 Chevy 235 cu. in. inline six? Mine has an 848 head on which a previous owner had installed umbrella type seals. The valve guides are worn pretty badly and will be replaced, but I don't know if it's better to stay with factory-type O ring seals or positive seals. Also I don't know if valve seals are recommended for both exhaust and intake valves. I would greatly appreciate advice from someone more familiar with these engines than I am. Thank you in advance!