The interesting question What are the most difficult challenges SpaceX will face getting astronauts to Mars by about 2025? links to Elon Musk's position paper Making Humans a Multi-Planetary Species which can be found (in both HTML and PDF formats) at:
Figure 9 gives you a more direct comparison. The thrust level is enormous. We are talking about a lift-off thrust of 13,000 tons, so it will be quite tectonic when it takes off. However, it does fit on Pad 39A, which NASA has been kind enough to allow us to use because they oversized the pad in doing Saturn V. As a result, we can use a much larger vehicle on that same launchpad. In the future, we expect to add additional launch locations, probably adding one on the south coast of Texas, but this gives you a sense of the relative capability. However, these vehicles have very different purposes. This is really intended to carry huge numbers of people, ultimately millions of tons of cargo to Mars. Therefore, you really need something quite large in order to do that. (emphasis added)
It's an interesting read, and a good way to start to understand the issues involved and how SpaceX amy approach them. However one item caught my eye. Stating that the proposed ITS rocket design (now downsized to the Mars vehicle version of the BFR (Big Falcon Rocket)) would fit on — and presumably be launch-able from — NASA's Launchpad 39A, it mentions in passing that NASA "oversized the pad in doing Saturn V", and that as a result SpaceX will be able to "use a much larger vehicle on that same launch pad."
Question: I am wondering if there is any information, or even educated speculation about the thinking at the time. Was 39A simply over-designed for Saturn V's weight and thrust out of an abundance of engineering caution, or was it in fact built to be able to accommodate a rocket substantially larger than Saturn V?
According to the linked article and Figure 9 (shown below), SpaceX believes, and presumably NASA agrees that 39A (of course with suitable modifications to some systems) should be able to handle a rocket with about 3.5 times the weight and 3.6 times the thrust of the Saturn V.