Does anyone know of a fuctional replacement for the 4 x 10" am/fm (not stereo) dash speaker for 67?

I don't know off hand, but you might try MCM electronics. They used to have a pretty decent assortment of speakers of various types. Perhaps you can find one that will work. http://www.mcmelectronics.com/

Some of the resto houses do have/carry dual speaker replacements for the center dash speaker.