You can land on the moon with 60s technology, what basis is there for not being able to reach that?
In space flight some of the most advanced technology even to this day was developed in the 60's and 70's. Things like NERVA[1], the NK-33[2], and the Saturn V[3], were developed back then and are still more efficient or bigger then similar technology we have today. The 60's and 70's were the golden age of spaceflight.