Posted on behalf of Nora Dempsey, who has recently worked with a refrigerator vendor to establish Harvard Library practices for our emergency freezers:
A 1970s fridge would almost certainly have Freon, which is non-toxic, (but maybe flammable?). Since I assume you aren’t running the fridge, it might be best to have someone come in and drain it. If they aren’t able to ensure that it is empty of chemicals, I would recommend being sure to transport and store it upright, and keep some sort of clean paper/board underneath it to easily monitor for leaks.
Again, assuming it has been off for some time, you probably don’t have to worry about moisture inside, (keeping the doors open, etc.), but opening it and taking a quick look/smell might be a good periodic check, as long as there are no concerns about the doors functioning. Along those lines, otherwise ensure that the storage environment is solid – dry and a reasonable temperature.