For folks that were around then as I was (and also impacted because my engineer father was unemployed for almost a year), this is not the worst in GM history. 16,000 were terminated back in 1974. Unfortunately Ford and Chrysler were hit too so job market was horrible!
https://www.nytimes.com/1974/12/19/archives/layoffs-at-gm-to-rise-by-16000-output-cut-planned-in-first-quarter.html