A few more points in regard to the 1967 Door Speakers :
1) A further look into the 1967 Door Speakers in the 1960-68 MPC, shows that the mounting screws have an "S2" (Raven Black) finish. Unfortunately, the Assembly Manuals tend to show an "S" finish (Plain) for virtually everything. I don't know whether or not they knew at the time the drawings were produced what the fastener finishes would be, or what, but I've found this to be the case on many occasions.
2) Another interesting thing from the 1960-68 MPC (specific page dated "April 1968), is that it shows that both the C6ZZ-18808-A Door Speakers (for 1966 AM-Tape Player) and the C7ZZ-18808-A Door Speakers (for 1967 AM-Tape and Hang-On Tape Player) were available. However, in the July 1968 OSI Catalog, it shows that the C7 was "Replaced by" the C6. I have known this for years, and of course it has helped me in procuring the two NOS C6 Speakers that I have for my '67. I have always thought that all Ford did was add the "captive nuts" and the "Protective Shield" to the C6 Speakers. But, in looking at the 1966 Door Speaker mounting hardware, it calls out for Part # 50438-S13 screws. These are # 8-32, Phillips, Oval Head Machine Screws, 1" long and Chrome Plated (chrome because the heads show in the surface mounted Speaker Grills). As no nuts are shown with the screws, this tells me that the 1966 Door Speakers must also have had the "captive nuts". Then, the only difference must have been (?) the addition of the plastic "Protective Shield". This of course brings up another question - why then, wasn't the C6 Door Speaker "Replaced by" the C7, instead of vice versa ? The only thing that I can think of here, is that on all of the 6 original C7 Door Speakers that I have had, the speaker frames were either Zinc (or Cad) plated, and the NOS C6 Speakers I have are both painted Black. A "Cost Saving" issue possibly ?
3) Finally, as a matter of interest, both the Installation Instructions for the Hang-On Tape Player, and the 1960-68 MPC, note that "if car does not have moulding" (Lower Door Trim), Dealer is to "obtain from Service Stock". This agrees with what Bob Perkins had told me over 30 years ago when I asked him, knowing that I would someday be installing the 1967 Hang-On 8 Track that I had on my '67, what should be "correct" for the Door Speaker Grills. He noted that he had seen on cars without the Interior Décor Group, both ones with the Lower Door Trim added, as well as ones using 1966 surface mounted Speaker Grills. Now, having acquired the original Installation Instructions as well as the 1960-68 MPC over the years, I think it can safely be said that Ford's "intended method" was to add the Lower Door Trim for the Speakers. Based on Bob's observations, there were apparently some Dealers who either didn't have the Lower Door Trim in stock, or just elected (due to time and/or dollars) to use 1966 Speaker Grills (there were no separate Door Speaker Grills made for any 1967 Model).
I trust this has been informative. I believe it pretty well covers all that I can add in regard to the 1967 Door Speaker Mounting and Speakers.
Bob