I have a 1980 ford f150 4wd that the ignition seems to shut off while driving. I've replaced the ignition lock cylinder but didn't help. Any helpful advice?

are you able to make it act up while it is at the curb? Then, what does it lose ? spark to the plugs? fuel to the carb? or battery power to the ignition coil? Try the primary tests if you lose power at the coil. After 30-35 years or so, you must verify what you have, then watch it die, then see what it loses, then test inspect and restore it. Note changes that were made to it. Books for the testing are available at some libraries, others have them at request. the older books were often donated to them for your reading pleasure. A worn ignition switch could be the result of your testing, or, if you had some mechanical issue with your link to the ign switch, you could start it while you had the switch removed. take things apart if testing leads you there. The best course is a tech of course, use the force.