July-Aug was the model year change over period. Old year models were winding down in July to gear up from new year model to start in Aug. Also GM woudl shut down for several weeks in July for maint. and vacations etc. They still do that, 2 weeks down in July.
LA also built Impala models along with the Camaro
Norwood was only building the Camaro in 69
Van Nuys built 32 Chevrolets per hour, half of them were "B"-bodies (Impala/Caprice); Camaros were about 16 per hour, or about 250 per day (vs. the 912 per day at Norwood).