Just an update on the problem. First, thanks to all that responded. After talking to folks alot smarter than me, including an electrical engineer, we decided to try something completely unorthodox....
I ran a ground wire from the negative side of the battery to the base of the starter solenoid. The thinking here was that possibly there was insufficient ground allowing the solenoid to 'hang up'. Yea, I know, Ford didn't run a ground to the base, but it was worth a try. After running the ground wire about a month ago, I have not had the thing act up again. I'm not about to say it's cured, but it has worked perfectly since then.

Go figure.

Again, thanks for all the thoughts and advice.

Yea, they were tight and in good shape. Since this car has been repainted underhood, I guess it could be possible that maybe there was paint under the soleonoid base, but you would think that the screws would have been ground enough. I like your idea of welding the nuts on the backside. I guess I could replace the screws with bolts, but I guess I'm kinda funny about using original fasteners.Anyhow, for now, I'm gonna run it with the wire in place for awhile and see if it continues to behave itself.
Thanks

Poor grounding is a common electrical gremlin.  It's a good idea to use an anti oxidation compound on electrical connections (including grounding points), especially where aluminum or disimilar metals are bonded together.  it also acts as an anti sieze.  Typical "antisieze" that is used for automotive or "bolting/securing" applications is not a great conductor but is better than nothing.  most starter housings, and bellhousings are aluminum, which is a good conductor when "clean" but when exposed to the elements will corrode and develop an oxidized coating.  Aluminum oxide is an insulator, so current path integrity is diminished.  A big reason that it's a good idea and common practice to swap out the original ford aluminum terminal  dizzy caps with brass terminal pieces.  Copper & brass oxidation is still conductive. 

The sheet metal screws that attach the solenoid to the inner fender provide the "ground path" for the internal coil of the solenoid.  the "ground path" for the starter itself travels from the starter, through the engine block, and through the negative battery cable from the block to the battery.  good clean connections where these components bolt together is critical to long trouble free operation.  going to larger cable size helps to.

Last edited by Nasty65 (12/13/2013 6:09 PM)