Space Duster speaker location

Was thinking about my 75 Duster Custom I had in late 80's, it had the space Duster option(fold down back seat). I was trying to think were the stereo speakers were(had a Pioneer am/fm cassette). I'm thinking the door panels weren't butchered for speakers, and I don't recall having surface mounts. In 75 would they have had a factory provision for stereo speakers.
Thanks
Aaron