Looks like T44N and R35E is the spot.  Now I will just magnify that area to look closer. ok, did that... didn't learn anything, but that 6X6, 36 Sqare mile Township is most likely the right spot for Thacker Pass, if I read that map correctly.  It just shows it as BLM land and shows nothing else.  Montana Mountains on the North and Double H Mountains on the South.  Nothing new.