1994 Ford F150 Ignition Problems

I have a 1994 F150, 302. For the last 2 months it has had a miss, like a bad plug, but it doesn't happen all the time. Some days it will miss first thing in the morning all the way to work. Some days when I leave work it will miss until I turn it off, start again after a couple miles and runs perfect. It did not have a miss at all today. Other days, I crank it, runs fine for 2-3 minutes and then starts missing. One person told me a bad pick up coil in the distributor......another said maybe the ignition module.
I would greatly appreciate any help on this.....and Thank you in advance.
Scott