To summarize, so if I trundle to my local Toyota dealer and have him order a 87940-60372 and a 87910-60142, I will get a left and a right 70 series mirror, whose base won't quite fit a 60 series door, but whose screw holes will line up. They will come with gaskets. Both will be flat (not convex), correct? It would seem that a custom base adapter would be relatively trivial to make, out of HMWPE or a chunk of a thick semi-trailer mud flap.