I will await reading your reference that describes field of view requirements when you find it. However, the AC does address the issue and says more than non digital clocks are OK:
6. INSTALLATION CRITERIA.
a. A display of hours, minutes, and seconds may appear simultaneously or be individually
selected.
b.
The installation should be accomplished in accordance with the current edition of
AC 43.13-2, Acceptable Methods, Techniques and Practices, Aircraft Alterations. In addition,
the clock and airframe manufacturer’s instructions should be consulted.
c.
The clock function switch position identification and the digital readout should be
readable in all lighting conditions from the pilot’s normal position