No mention of the tachometer change has been noted in Chevrolet service information.
A late change made to the 302 engine assembly was the substitution of the 1112003 distributor in some cars, probably done to consume them. 1112003 was intended for the '70 Z28, only known difference was an RFI shield. During research for the CBTN books, Al Colvin found an accounting document for 1112003 at a Delco plant, noted OBSOLETED OCT 20 1969. I don't believe there is any mention of it in Chevrolet service info.
Some late production Z/28s received dripper rocker covers.