Here is a December 1969 factory manual of Working Times for Porsche 911, 912 and 914 models, with some updated sections. It details the factory labor rates book, and it does break down the assembly times.
The manual is in good condition. 1d.jpg1c.jpg1a.jpg1b.jpg
If more pics are needed do let me know.
€225 ONO plus shipping
Manual is located in Europe
Thanks