Good job! Next, take your rocker shafts off and clean out all the oil holes, in the rocker arms and shafts. CLICK HERE
Back in the day we used non-detergent oil. Sediment filled the rocker arm holes and eventually plugged them. A small drill bit or stiff steel wire will open them again. Old stagnant oil remains in the shafts that turns to light grease. Be careful, it will not come out of your clothes. This cleaning costs nothing to do. If you find your shafts are worn, they are available at the parts stores.
I never liked the 'umbrella' seals from back in the day. They harden, split, travel with the valve stem and sometimes they break. In any case, they sure don't do a very good job of holding oil back.
Modern heads use Viton seals. They have a circular spring that holds them on the tower and they don't harden. The old stuff was made from straight neoprene.
Keep up the good work. - Dave