The Ford Point Richmond CA assembly plant, built in 1931 has been restored, it was well preserved prior to that..if you ever get out to San Francisco it’s worth the trip .. the assembly hall has spectacular views of the SF skyline, and was used in the movie “Tucker”..
The original T plant in downtown Los Angeles now houses Warner Bros Music. The replacement plant (1932?) in Long Beach harbor was torn down in the 1990s to make more empty land in the port. The Pico Rivera plant (1957) that replaced it was sold to Northrop Aircraft. It's where they built the B2 Bomber. It's gone and now a shopping mall.
GM had a plant in South Gate (Caddy) and one in Van Nuys (Chevy) both are gone now. Van Nuys is a shopping center that kept a little GM looking heritage.