The date codes on the sheet metal parts are many times incorrect. I was a tooling engineer at a stamper that supplied Ford, Toyota, Nissan, Saturn, Dodge, Chevy, Lincoln, Honda, Mercedes, BMW, John Deere, Husqvarna and others. They all had their unique date codes or ID markings. Many times our guys would put the wrong number / letters in and they made parts. Parts might be missing a hole or have a burr and go to the rework area and depending on how much work they had could sit for months in the warehouse. They would put the hole in or grind the burr off and ship the parts. Then the fable of the date codes on all the panels being close to same time goes away. The date code would be months back but would go on with recent date code parts. You could even have a date code after the car was built if the die maker put the wrong stamps in.
On the service parts. Once a part went out of production you would grease up the tools and set them outside. Some would never get ran again. Parts in the front and rear of the car were always having to go in for service runs. It could be a 100 parts or an agreed minimum order. Lots of the automotive service parts were produced by Gerstenslager that was owned by Worthington at one time.
I had an order come in from Ford once for the inside back for the Model 10 or the standard cab for the Ranger. They were going to use the old parts to make a crew cab version for South America and needed parts for prototype. We had just ran a couple hundred and sent to Ford about a month before. I called the engineer and told him they had parts in service but he wanted raw steel parts no ecoat. So instead of going through all the trouble to pull the tooling in from the yard, clean and set up the tooling again I ordered the parts from Ford stripped them and sent them to Ford and they were happy.
I saw a comment about running stainless in the tools would trash them. I do not know why it would. We were also the largest manufacturer of beer kegs in the U.S. and they are stainless and the tooling is usually bronze to prevent scratches in the food container. It does take more draw cushion pressure to draw stainless but it will not kill the dies.
Automotive volumes are pretty low by other products out there. We made lawn mower parts for a couple different plants and some made 5,000 riding mower units a day not a few hundred like automobiles. They would make 20,000 push mowers in a day. You could run millions of parts off tooling that was properly built. Not many cars ever made a million of a model in the life of the car. We had to warrant the dies to produce one million parts for the mower companies and then they would pay for a rebuild.
I worked my last year as engineering manager at a tool & die shop in China. Everyone thinks they work on dirt floors in dark holes. They have much better equipment and shops that I see in the U.S.. Sad to say but true. Now getting them to do what you ask them to do is another subject.
David