Unfortunately too few people have a good grasp of how vehicles are, and were built, and that causes what can only be called the "rumor mill" to fill in the blanks. It is unfortunate but easily corrected by disseminating correct information.
A common misconception is the idea that Ford used left over parts from previous years or anything laying around to build vehicles and that is a myth. Yes, it is common to have parts that are considered one years parts on the next years vehicle but that is not because they were leftover. The only way they can be used is if they are scheduled to be used. For example, the air cleaner on a 66/67 352 in an F100 or F250. There were two different ones, C6TZ-9600-E used before serial number A84,001 and C7TZ-9600-G used from serial number A84,001. You may find a 67 owner saying "my 67 has a 66 air cleaner on it". Technically this is true but only because that was Fords plan. At a certain point in the production cycle Ford changed the plan and started using a different part. These running changes were actually quite common and well documented. It was, and is, critical for Ford to know what parts they built a vehicle with because they had a warranty. When a vehicle was being serviced in the field, the dealer had to be able to order the correct parts for replacement.
Another issue was failure, Ford tracked parts failures in the field like an jaguar tracks prey. They used this information to identify problems and issue recalls. It is truly amazing to read through 1960's NHTSA recalls. There are some astounding examples. Recently I came across a couple of fine examples of just how accurate the record keeping was at Ford. Due to laws regarding manufacturing, warranty repair demands and insurance requirements, Ford really did (and still does) an incredible job tracking the parts used to assemble a vehicle. Fords JIT inventory system was one of the best in the world back in the 50's and 60's and it was highlighted for me when I was reviewing the old NHTSA recall information. Did you know there was a recall on 67 Mustangs for body issues? The amazing thing was the records indicate that it affected 842 cars! Tell me how much more accurate you can be? Given the several 100,000's of cars made, it was amazing to see that small number. I looked at a bunch of recalls and they usually affect 10,000 20,000 even 400,000 cars but here was this recall for 842 1967 Mustangs. For comparison, the recall for 68 Mustang seat back failures was estimated to be 480,000 units and 67 Mustang steering wheel recall was 447,000 units. Another good one is the 69 Mustang heater core which affected 12,972 units. The fact is Ford knew specifically how many vehicles were built using a specific part although they may not know exactly what serial numbers they were because of the way inventory systems works. Ford would know when the parts were received but not when they were actually used beyond a margin of error (that is why recalls always say between XX/XX/1968 and XX/XX/1968).
I realize this is long winded and meandering but I feel it is important for people to have a clear understanding of how things were actually done not how urban myth has come to be accepted as "the way things were done back then".
