Both seals will be included in an overhaul gasket set from FelPro or others. They are likely just old and worn out. Remember that the rubber used 53 years ago was not as good as todays seals. The rope seals are famous for leaks. Your engine is the full pressure 235 and was first year for that but that doesn't explain the leaks or all old GMC's would be leaking for that reason alone. Also w/o the full filter of modern engines there was a lot of dirt and contaminents in the oil to increase the wear factor on the seals. At least that is my theory and it explains it to me so I'm stickin' to it.
