My guess is the the hours given in the old shop rate manuals are likely meaningless. Even back in the day as my old long serving GM trained and expert mechanics friends would say, they often ran into problems the time and motion studies used for the manual and used as a basis didn't experience some of the real world difficulties the line guys had to overcome. In fact we discussed a similar case just this morning at our weekly coffee club. Given the years since new and no telling who buggered up stuff or how they "fixed" their buggers it will likely take the time it takes.
