1967 A-body Big Block 383 4bbl 727 Automatic Transmission

Since the build date started on 7-29-1961,0001 and ended on 12-13-1988 at 9999,I see a problem,Since I have some 30 automatic and standard transmission in stock,and alot of them pre 67,with propper date codes on them,I still have questions,mrmopartech
1968 dart 383 automatic transmission number PK2892031 used on ABC cars
I have 1 other pre 66 tranny with the proper 17 digit code,2 letters,7 digit serial number,4 digit build date,4 digit sequence number.