even in 1970 the technology was ready for to get to Moon and land with LH2/LOX (3-4 day)
there were proposal to replace LEM step by step with LH2/LOX tech.
source "Improved Lunar Cargo and Personnel Delivery Systems," by L. L. Morgan and Rodney W. Johnson
found at Romance to Reality: Moon & mars mission plans
reborn as Altair VI Blog