Actually just the bodies were produced in Flint then trucked to Pontiac, Mi. where they were mated to their chassis and completed. Then complete GN's were trucked to the ASC/McLaren plant in Livonia, just off I-96 for their conversion to GNX's.
I believe the address is 34165 Autry St, Livonia, MI 48150
Both of the GM plants where the cars were assembled have been torn down.