Nahuatl-Cora/Huichol separation

[ECOLING at aol.com]

Someone asked me privately,
and rather than look up in some reference work,
I thought I should ask this list for the best current views.

At what date is Nahuatl supposed to have separated from
its closest relatives in Uto-Aztecan, Cora and Huichol?

Would that have been in the location where Cora and Huichol
were at time of contact with Europeans?  Or did they separate
earlier, and both continue south along the Cordillera to
their positions more or less at time of contact with Europeans?
Or some other scenario?

I assume Cora and Huichol are still regarded as the closest relatives
of Nahuatl?

Thanks for any enlightening comments,
either on the list or privately.

Sincerely yours,
Lloyd Anderson