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It sounds to me like a fuel pump issue. The fuel pump on the 1995 f150 was pretty robust and would rarely fail all at once; rather it would stop working and then start working randomly. I would assume that it acts up when the temperature changes. I.e. worse when it's hot, better when it's cold. To test whether the fuel pump is the problem you need to wait until it won't start and then have someone turn the key to the run position while you listen for a buzz at the fuel fill neck; it should buzz for about 3 seconds each time you turn the key. If you can't hear the buzz, the fuel pump is likely the culprit. A thump or kick on the fuel tank might bring it back to life temporarily but it will eventually need to be replaced. Or you could hook up a fuel pressure tester and see what kind of readings you get.
Are you getting a spark when it won't start? You could pull off a plug wire and hold it close to any metal ground and see if you get a spark from the plug wire. You can shock yourself this way so use caution. It won't kill you but it hurts like crazy.
If you don't get a spark you might check the distributor pickup. They occasionally go bad, or out of adjustment. You can test it by checking for a AC Hz with a multi meter from the pickup connector while you crank the engine. If you get a reading, it's working. If not, it needs to be replaced.