Well I looked around a tried the fit of a few against a removed Nakamichi speaker. Thought I had one with the pioneer 4in at circuit city but the 4 mounting holes don't line up. SO I tried the Boston S45 in the rear and good fit. The connections have changed since 1995 so you will need to splice the negative (white with black) to make a good commection. The boston are a little deeper but it does not matter in the rear. May matter in the door but dont know. The sound is good but I am not an audiophile. The cost was $99 for a pair but there is probably a better cost out there.
There are great link and info on the forum already on how to get access to the speakers
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Norm