I don’t remember the lunar lander, but I do recall reading how each rocket engine on the Saturn V was one of a kind, because the engineers had to assemble each one by hand, and each acted slightly differently. So there’s no way to reproduce a specific Saturn V engine now, but there also never was back when the Saturn V was still flying.
Genuine question: How is this different from a F1 engine where each piston head is crafted for each cylinder in the block? When you go high performance things that look like they're a commodity become one-of-a-kinds as you push them right to the limits.
Would we do any differently today? I think we gravitated towards smaller and more numerous engines (that are easier to construct to the same exact copies), but nobody since has built anything remotely as large as the Rocketdyne F1.
These days we have computational fluid dynamics. We can simulate many more things to make an easy to build design rather than making manual adjustments to each one.
There’s been little need for a liquid fuelled engine that large though due to advances in solid rockets in the US and Europe, and a focus away from super-heavy launch vehicles elsewhere.
You'd have to redesign it from scratch - it would be faster. Which is what happened with the SLS engine/launch vehicle.
Duplicating the F1 would involve technology and knowledge of individual engineers who are dead and corporations that no longer exist. The TACIT knowledge and technologies required to go with the blueprints died with them.
SpaceX pursues its business on a much larger and, most importantly, more regular schedule. In this case it is possible to standardize and mass produce many parts.
