Most of the parts, except trivial stuff like oil filters and tires, can't be had new because they haven't been made in years. Think of the factory production lines that would have be set up to make everything from wheels to pistons.
That's the vintage of equipment and engineering practice we're talking about.
Yeah, exactly. There’s really layers and layers of grossly post dated technology.
There was a guy on the net about 10 years ago, I could probably find his stuff on YouTube, that really dug into the tech that makes the that makes tech. His angle was post apocalyptic recovery. But it was really informative and helps you understand just how many layers deep we are on these things when the guy goes into all the machines necessary to make a pencil and just how much infrastructure a society would have to rebuild to get to making pencils again.
Once you start looking at that stuff you can really see how old technology gets “lost”. Once one thing in the manufacturing chain has advanced too far to make this part for the Saturn IV (or a part used by a thing to make a part for another thing to make a part for the S-IV) because it’s post dated, boom that whole chain is lost.