I'd assume a single ply coated head, tuned really loose, with some muffling.
Keep in mind on Rumors, the drum tracks were bounced down several times (the equivalent of copying from one tape to another) which causes a loss in sound quality. This happened because Lindsey Buckingham kept adding more and more layers of guitar and vocals, but technology at the time didn't allow for the sheer number of tracks we have today, so he kept condensing the drum tracks, which really affected their sound.
If I were really trying t re-create that sound, I'd probably start with a two ply coated head to compensate for all the various micing and recording techniques they used that would be impossible to re-create.Tune it low, and experiment with muffling until it sounded right.