Lesson learned, when troubleshootin g  an intermittent fault in the starter circuit ensure that the starter is bolted on tight. I had changed the starter solenoid once and was getting ready to change the starter switch in the steering column when as I was turning the car over with the key I heard a bump,as if the starter was loose so I got the car on jacks and sure enough the bolts had backed out causing the problem. So in the future when checking an electrical problem like the starter ensure EVERYTHING is tight not just the easy stuff (battery cables etc).The trouble shooting guide is great but I do not think this is in there.One more thing if you have Motorcraft parts keep them, the stuff made in China had cause the starter Bendix drive to continue spinning of which is not a good thing.

You can also rebuild your own parts, if the starter Bendix drive is not bad or the alternator is stator is not bad and even the bearings in both can be changed. Haynes has a book that shows how to do most of the rebuilding process in detail.