Exactly. On some machines, you would find a head that was merely a shell, that is, no recording coil, no pins. These would go in the first position, where the record head would sit, in order to guide the tape properly to the playback head.
As time wore on, this head would be grooved, so it would not be unusual to find a worn (but not grooved) playback head moved into this position when a new head was installed in the playback position.
Would be unusual to find an eight track head, since they were designed differently than cart machine heads. But I suppose it would kind of work. Typical cart machine head is either 2 track or 3 track (stereo plus cue track). All work in conjunction with the guides to insure proper tracking across the playback head, critical for stereo, since the tape carts have very little tracking guidance.