I had to pretty much dissassemble my rear seat to get to the rear-speakers... I know it sounds crazy, but that's exactly how it's got to be done. Get a copy of the Haynes auto manual for 92-96 Camry's...it explains in detail how to get the rear speakers out. It was a pain to do.
I replaced my cheap factory Fujitsu's with some nice 6x9 Polk 3-ways (dB Series) They fit fine, but I had to make my own clips to mount in the factory screw holes.
Good luck!
Don't know if this will help, but here's some pics I took during the process:
1. El Cheap factory units:
2. New Polk dB in rear deck opening:
3. Rear deck and Rear seat removed with new speakers in place:
4. Another View
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The 'Work Horse' - 1993 Camry LE V6

The 'Stallion' - 2005 Mustang GT

The 'Wife's car' - 2009 Highlander Sport