Back in the 60s/70s, it was not possible to do an automatic hook-up of modules in space.

Well, maybe not for Americans. The first Soviet space docking (October 30, 1967, a year and a half after the first US space docking, with Gemini 8 on March 16, 1966) was between the unmanned Kosmos 186 and Kosmos 188 and was automated.

Soviet moon missions using multiple launches and automated docking were considered, at least briefly: http://www.astronautix.com/articles/theoblem.htm