Very interesting discussion, gents!
I went through four starters including the Motorsport, Nippondenso and another geared starter whose make escapes me.
The one that fixed my problem is the good old 1995 F250 460 starter.
The car has a C-6 so only the stock bellhousing is involved.
All of them worked at first! The symptom that developed after I'd used the first three starters for a week to three months, depending on the starter, it would start going "click" instead of engaging and starting the car. Interestingly, if I jumped the car from another car's battery they would often start. If I used one of those portable starting devices, it would not start.
I replaced starters, batteries, ran extra grounds (probably have an extra 50 lbs of grounds in the car now
), rewired the starting circuits - no luck. After a time the dreaded "click" would occur. Never regularly; usually when the car was hot, but seemingly at random - it would work fine for a week or so, then "click" and refuse to start.
Along the way I bought a starter from a guy in South Carolina who forgot to send me a shim - SCREECH - several phone calls later I learned about depth of tooth engagement.... A 0.050" shim solved that one.
Finally over at 460.com most of the guys suggested the plain old Ford pickup starter - it weighed less, cost less and has worked perfectly for longer than the prior three units put together.
BTW, the "click" seemed to result from the geared starters' blunt teeth. After a time the starter's pinion teeth seemed to "flat-spot" on the leading edge. When this happened, randomly I might add, SOMETIMES the starter could not pull into engagement, and when that happens, the motor windings never get energized, so the pinion can't turn. Then "click" "click" until you want to put the thing into Viking Funeral mode....
Maybe this helps, maybe not!
Tom