The undercoating package was more for sound deadening then rust protecting. If you think of it that way, it makes sense for the hood pad to be included with the undercoating.
Most cars that had that package came with a molded hood pad. Some came with a non molded/generic insulation pad. There must have been different vendors.
If you don't have your fender tag or build sheet, look for the metal clips on the underside of the hood. If you're car came with one, the clips might still be there. Your 71 should have metal clips...they changed to plastic clips on the later years.
