Remember that Empeg isn't the only aftermarket-stereo-maker out there. Everyone (clarion, sony, pioneer, rockford fosgate) makes their stereos DIN-size.
So, by making a custom non-DIN dashboard, the car makers aren't just dissing Empeg, they're saying "screw you" to every aftermarket stereo maker out there.
BUT... Having said that...
You would be surprised at the ingenuity and resourcefulness of the aftermarket-stereo support chain. Often, what looks like a totally proprietary dashboard can be easily adapted to DIN just by purchasing a third-party adapter kit. Some kits will be more complicated than others, depending on the vehicle.
Just for grins, call Crutchfield and see if they have anything for the particular models of vehicles you're referring to. Make sure to
call them, don't just go to their web site. You might be surprised by what they tell you.
Finally, a good custom installation shop can fabricate whatever they need to make your stereo work in your dash. It might not be cheap, but it can be done.
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Tony Fabris