Picked up a toploader I need to ID

[DanEC]

I picked up a toploader trans for my ERA Cobra and it's missing the ID tag. It's a small spline WR transmission with a short tailshaft. The small input has a long pilot bushing snout. Case number is C5AR-7006-D and the tailhousing is C4ZR-7A040-A. It looks like the date code on the trans case is HB. It looks like there is a yellow 6M stamp on the driver side of the case. The M is distinct but I'm guessing a little on the 6.

From the charts it looks to fall in the 67 to 68 range and probably out of a Mustang or Couger.

Can anyone pin down closer what this might have come out of?

Thanks

Dan

[DanEC]

Related to this transmission I noticed that the pilot nose on the intake shaft has some wear from about 1/2 inch to 1 inch from the splined section. It measures about .003 less dia than back by the splined section (about .0682 versus .0655). Since I'm going to have to cut the shaft shorter to mate up with a FE block crankshaft most of this will be gone. I'm not really seeing this as a big problem - is it???