yes they are date coded , I have a page full of dates I collected over many years of buying Camaro shifters
the 68 69 Firebird used the same shifter but a different date code
Camaro used 6 or 7 characters
Pontaic 4 or 5 characters on GTO and Firebird Hurst shifters
there were also replacement shifter and those codes don't fall in with the assembly line shifters
common 69 camaro examples are 29D21C feb 1969, 108D41C Oct 1968
68 69 Firbird example 88D4 Aug 1968 , 98B5 Sep 1968