1968? I'm guessing NO. A lot of stiffer regulations have been put in place since then. You probably have particle board sub floors and I hesitate to think what size floor joists and wall studs you have. Of course, being that old, there could have been major modifications over the years and only you know what you're dealing with here. I would take a good look at what you're dealing with structurally before adding that much weight to your floor.