All 1969 Yenko's were 9561's and 9537's
NO RS YENKO's in 1969...
Gary,
The 9561 triggered an exception or modification of the L78.
There are sheets from GM showing the deleting of emblems and engine CUI call outs.
The reason they started with the L78 was it was the easiest way to get the correct suspension and other items, XT wheels etc.
The 9561 added the ZL2, L72, and HD 4.10 which also triggered HD cooling (curved neck radiator).
The 9537 added the 15" wheels and the 140 speedometer.
As far as the lower black out goes... it would have only been an issue on the initial 50 cars as they were the only X66 coded Yenko's.
The remaining 150 cars were either X11 - lower blackout or X44 no lower blackout.
One could imagine if Fisher Norwood were the final assembly point then the first 50 may have received black grilles, however Chevrolet Norwood was the final assembly point and thus we are not faced with that quandary.