Quote:

a) Is the factory opening dual DIN, or is it 1.5 DIN?
b) Has anyone succeeded in getting two DIN units installed?
c) Is there a special mounting kit that can be used to get dual DIN working?

a) It's not either. Just a bit less than 2DIN though.
b) Yes. Me. Kinda.
c) No.

What I ended up doing was duct-taping the empeg cage and the HU so that the faces would be even when viewed from the side. Then I took a piece of metal and screwed bolt into the back of the cage and HU so the rears were secured together. The time consuming part is taking the stock HU apart from the two side mounting tab/brackets and mounting them to the Alpine HU's side screw holes. It takes some time to line it up right but once you figure out where to drill the holes you're good to go. The flash in the pic below really makes it look crappy but it does look cool when it's view under normal circumstances. I'm actually going to modify this further soon so the two units will come out a bit further and be closer to me.

The only thing was that I had to trim off the lower section of the Alpines trim bezel: