I have a '98 Forrester, and just dropped a Mark2 unit into it.

The Subaru factory head unit was a Clarion unit, with a 13-pin DIN
connector at the back for expansion (CD changer, etc..).

I deciphered the pin-out of this DIN plug, but it was of no use..
one of the pins is a 2-way intelligent "logic" bus, which basically
prevents use of the expansion connector with non-Clarion components.

So I set off in search of a new head unit, but discovered that nearly all
current ones on the market (Canada) also have proprietary expansion
"capabilities". Found one exception (so far): JVC KD-SX850 radio/CD
head unit has generic "Line-In" RCA jacks on the rear. Whew!

I promptly purchased the JVC, which fits neatly into the same slot as
the original Clarion unit, and then installed the Empeg Mk2 below it.
The Empeg is wider than the original mounting "cage", but this did not
present any problems -- the cage metal is easily flexed/bent by hand
to accomodate.

I used a strip of sheet metal wrapped under the Empeg to secure it
to the underside of the new head unit within the cage.. friction fit,
but it won't budge now!

Rather than a Dremel tool for cutting the dash trim piece,
I used a combination of an electric scroll saw and a sharp
knife for most trimming. Looks Great!

-ml