Everything was sloppy on the line building those cars. Look at the way all sealers were applied. Caulking in corners was pushed in by a cotton glove covered finger. Spare bolts left under carpet, candy wrappers are a common find in unmolested cars.
Consider this, 500 cars per day at each Mustang factory in that era, that gives 2.88 mins per operation on average. They must have been many lines at each plant as I know that paint inc rubbing & dry time, took about 1 hour, installing headliners took 1.5 hours, just to name a couple.
Thats why when you see pics of the production line from those days, usually the operator was holding a hammer! There is a good shot of a worker "adjusting" a hood in the Mustang Recognition Guide that has been around for years. We have seen front guard bolts in unrestored cars that have been punched down to get a good bonnet fit.
An American friend of mine worked on the Chevy line in CA back in the 60's while going through college. He told me about saving time by using self tapping bolts in place of correct fine threaded bolts in the inner guard shells of Oldsmobile 442's he was putting together. He wonders how many of those fell out later!
