My solution for Wagons that came with only front door speakers.

I'll keep flogging this idea for older Wagon stereo upgrades. I think it is the ideal solution for and only requires a tiny slit in the headliner to accomodate the bolt thread. Rear Speaker mounting.
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For a wagon an option for rear speakers.

on either side in the rear of the wagon there is a metal post for the rear shoulder belts. Using the top of the post to measure... 5 inches toward the front of the car...under the lip of the headliner is a threaded mounting point for, if I remember correctly, an 8mm thread....I can take a hefty sized bolt

It's there for the Cargo/Dog cage accessory that can be added to the back of the wagon.

In the 2 wagons that I have owned I have used that point to mount 6 inch speakers.
Running the speaker wires from the dash under the front side carpet UP inside the plastic seat belt cover on the door pillars and under the liner.

Neither of these wagons originally had rear speakers and after looking at other options this proved to be the best solution, when I upgraded the stereo.

You of course need speaker enclosures...but with that stout mounting point you can hang a big box.
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This speaker position caveat... if you regularly have rear seat passengers, you'll have to balance out the Frt/Rear when they are in the car, as the speaker will be pointed at the passengers ears.


The speakers are high and out of the way. I've never had a problem loading the wagon to the gills. This is way better than a rear door mounting, since speakers mounted in the lower rear door would be blocked in a RearSeat folded Down fully packed cargo space position.