.. yes, they changed in74 MY to the Quartz Zeit. The Kienzle's were considered very reliable, but the quartz more accurate & simpler mechanism, which was probably cheaper, as was the change from glass to plastic gauge lenses on the 3 pod instruments.
North Hollywood Speedo & Palo Alto Speedo can convert the innards of the earlier 911/912 & 914 to quartz & keep/restore the face as Kienzle - if you're having any VDO instruments repaired &/or restored by them.
More good MY fitment info here:
http://p914.com/p914_gauges_clock.htmBTW - the Kienzle will probably have a bit more current draw - being mechanical - than the Quartz Zeit, for those who drive their 73 914's & others with the early clock infrequently, & don't use a trickle charger/maintainer