No doubt "legally" was often open to interpretation.  An old friend has a car clearly marked as not for highway use, but as it has a VIN, it has been tagged (and occasionally street driven) since the '70s. At this point I'd worry more about the insurance adjuster in case of a catastrophe.

THAT guy is the reason for degreeing every cam. 

I'm loving the updates and can't wait to see/hear the results. Thank you for posting your progress.

It's not happy and locked in that position by the lower link now. I wonder if it would return if you took the link loose and maybe even stay there if it was set up with the link just a little longer.

I've put lots of miles on the Snap-ons, and I like them, but they do have a tendency for the wires to break down inside the insulation where they enter the body. Often just a tedious shorten/solder job, but worth watching for in a used unit. It starts out with just having to tilt it the right way to operate.

Edit: Holy thread resurrection.

And if you just can't get enough side-oiling:

https://www.ebay.com/itm/427-Side-Oiler-FE-FORD-PRO-Stock-Engineering-Engine-w-nos-fit-Cobra-Mustang-/123761697828

If I've read this correctly, you're getting backlash measurements from .009-.015", but that doesn't fit at all with the issue of 1/2 to 3/4 turn of free travel originally checked at the yoke.

A couple of things come to mind. Is it possible the "slack" you were feeling wasn't gear backlash at all, but movement of whatever locker unit you're using while one wheel/brake was dragging a bit? Hope that makes sense. Otherwise, if a pinion bearing has gone south or your crush sleeve is "overcrushed" it may be that the pinion has somewhat "fallen in" at the moment, and your backlash checks are giving a deceptive reading at one end of the pinion's new "range."

You're getting great advice. I just don't see where the big slack was coming from.

I think I'd make absolutely sure the pinion preload is real. Even a couple of taps with a brass hammer in each direction front to rear to confirm it hasn't migrated.

Here's an approach you don't see every day. 

https://www.ebay.com/itm/1963-Ford-FE-427-Intake-Manifold-Possible-Ford-R-D-390-406-352/173962853927?hash=item2880fe7e27:g:gV4AAOSwd7RdKO6c