Absolutely, GM determined when a particular car was to be built based on their schedules, and their part availablilities and Fisher built it. There wasn't really much on the fisher side of the plant that could result in a material shortage that wouldn't alos affect the GM side. Maybe things like convertible and vinyl tops in certain colors, some interior peices, etc. Most of fishers parts were sheetmetal stampings that were not specific to a certain vehicle, like a 302 engine, or an M22 transmission. I'm sure there were some things on the Fisher side that could delay a build, but most of them was probably on GMs side.
So was Fisher sort of like a supplier to Chevrolet in that Fisher's production was to produce bodies for orders placed by Chevrolet?