As to the pushrods, the originals are not as good as the sealed power replacements. They are not that expensive so you might just want to replace all of the pushrods at one crack, readjust the valves and my guess is that the motor will continue to run well. If you do go to the trouble of pulling the head, you might as well just freshen it up while its off. If the valves are good, they just might need to be refaced. Then its bronze valve guide liners (don't try to replace the cast iron guides, you might break one or the head. Use the liners), have the top of the guide machined for new style teflon seals, fresh facing for the valve, fresh facing on the head and a good cleaning and assemble. Take a pass on hardened seats. You will never in your lifetime put enough miles on that truck to see any issues because of low lead. I just took a 235 motor out of my 57 that I beat on pretty good for nearly 30 years. None of those years did I have access to leaded gas. When I took it apart, the seats were just fine.
