There was a proposal to design an improved F-1B which would be much more simple due to advances in technology and produce 15% more thrust at sea level. From wha

There was a proposal to design an improved F-1B which would be much more simple due to advances in technology and produce 15% more thrust at sea level. From what I can tell the designs got rather far along but NASA ultimately decided to stick with SLS and shuttle derived hardware. SpaceX is all about reusability and they have determined that having a large number of smaller engines gives them better control of the rocket during boostback and landing burns. F-1 style engines seem best suited for big disposable first stages and no one in the private sector seems to want to do that. https://en.wikipedia.org/wiki/Pyrios https://en.wikipedia.org/wiki/Pyrios