I wondered why you asked so I did some research.
Maybe not everyone is aware, 6 cylinder and Z/28s used a reverse polarity battery + term on the left. No matter which battery or cable configuration was used, the - ground wire is terminated on the fender brace.
However for '68, reverse polarity batteries terminated on the core support. I assume you are wondering if this continued into early '69 production. The '69 AIM shows the fender brace termination but Rev 5 dated 3-3-69 states "NEG GROUND DWG REVISED." Doesn't state what was revised.
The late John Z once advised not placing much stock in the dates in the AIM. I checked the January '69 Hot Rod magazine road test of a '69 Z/28. Early Van Nuys car built on or about 10/1/68. Pic shows a reverse polarity battery, ground wire terminated on the fender brace.