Back in the early 70's Ford had a lot of trouble with their cast iron parts. Valve guides would wear enough to let the valve cock and not seat properly causing an intermittent miss. This was on engines with less than 12K miles (still under warranty). Ford's fix was to replace the head which may or may not be the same material. I got my hands slapped for sending a head to a machine shop and having a new guide installed. So Ford came out with a kit to drill out the old guide and press in a new one. There were a couple of bolt on fixtures to align with the center of the valve seat. You then used a 1/2 in electric drill to drill out the old guide. The local factory rep came to the shop and did an "after work" demonstration of how to use the kit. He then used a driver to pound in the new guide. The only problem was that the new guide fell through the hole he had just drilled. He packed everything back up and there were no more conversations about purchasing the guide tool. You still had to re-grind the seat after the new guide was installed. However, most dealerships had valve grinding equipment back in that time frame. We did a lot of valve jobs under the old 5-50 warranty. A lot of FE engines couldn't make it to 50K miles without burning an exhaust valve.