Re: Distributor gear fail
The symptoms you describe sound *exactly* like a distributor gear problem. And Jac Mac, over the years I've been around at least a dozen different distributor gear failures (none of them mine thankfully!) where the failure wasn't sudden and complete, but rather gradual and confusing; the car suddenly started running badly, but it continued running. (I've also been around a few failures where they suddenly quit stone dead, like somebody had just taken a poleax to the entire ignition system).
The two main types of failure are failure of the gear itself, and failure of the shear pin which attaches it to the driveshaft.
Fords use a gearrotor-style oil pump, which is basically two gears meshing together and squeezing oil through the system. Debris in the engine (deteriorating gasket, valve stem seal, excess silicone sealant, etc. etc.) can become trapped in between the gears and momentarily cause the pump to jam. When this happens, usually the shear pin does its job and snaps, and the gear is free to spin on the shaft, and the car simply stops dead.
But sometimes the jam is so momentary, and the gear is a press-fit on the shaft, so that the pin snaps, the gear rotates on the shaft and then grabs, and then the car continues to run, although the timing is now grossly retarded. Suddenly the car runs like crap, overheats etc. etc.
The other failure is simply one of the gear wearing out. Steel roller cams required a soft metal (bronze) distributor gear, which has a known sub-5000-mile lifespan. Just last year I helped bail out a Pantera whose owner had bought the car recently from an estate. It had a completely killer engine whose specifics were unknown, built to the hilt as a 'race motor' including 'race' parts, including a sacrificial distributor gear. The guy drove the car about 2000 miles without incident, then drove it in one day from home in Oregon down to central California where I and a handful of friends met up with him enroute to Las Vegas. The next day, it started acting up, and would barely run.
Eventually we managed to get it started, but it didn't have enough puff to negotiate the slight hill of a driveway. After fiddling with it for a couple of hours, we pulled the distributor and discovered that the gear was totally worn away. What was happening was that the timing was free to jump around, perhaps plus or minus 20-30 degrees from the proper setting?
The motor had almost exactly 5000 miles on it at the time.
Whether you've got a bad gear, or just a bad pin, I'm fairly confident you'll find that your problem is located there.
Just FWIW, Comp Cams has introduced a new whippy-dippy distributor gear within the past couple of years, that is an upgrade from the standard cast iron gear, with three times the lifespan of a standard bronze gear. Here's the relevant page from their catalog:
http://www.compcams.com/technical/Catalogs/106-07/235.pdf
Alternately, I've also seen the same problem caused by a timing chain that jumped one or more teeth. The stock Ford timing chains use cheap nylon gears, which have a finite lifespan. When it jumps teeth, you check your timing and find it drastically retarded, so you rotate your distributor and it's "fixed"--until it jumps again.
In any case, it sounds like a timing issue of some sort.
Good luck, and let us know what you find!