Howdy Back:
Ahhh! the worn end of the pushrod indicates a lack of oil getting to the front of the rocker shaft. You should see oil oozing from each rocker, especially the front as they are the last to get oil. Most likely the shaft, rocker holes are plugged with gunk and not allowing oil to the front, or more, of the rockers, pushrods, and the lifters below.
Remove and disassemble the rocker shaft and thoroughly clean it, inside and out. Make sure the oil holes on both sides of the rockers are open and flowing.
Seafoam will help clean out varnish and some gunk but it will not open clogged passages.
Check it out by removing the rocker cover, starty the engine and watch how long it takes to see oil ooze out of the front rockers. Any longer than a minute indicates a problem.
Adios, David