Please excuse my bumping an older thread; I hope to add to what has been said and, perhaps to the article on changing a 240 radio?
The ISO adaptor PC 2-52-4, as listed in the article is for later cars (Sept 1990 on according to
www.demonaudio.co.uk). The adaptor for earlier cars is PC2-20-4.
My radio also had a 4-pin grey connector, but nothing on the car, as it does not have rear speakers.
I ordered the cable from Demonaudio. their website does not show the square, four-pin socket for the rear speakers, but it is on the cable.
The rear fixing for the radio on my donor car ('93 Torslander)was a metal strip, with a tongue bent down (photo). This fits through the
slotted bracket shown in the article by 240. Mine was wrapped in gaffer tape, which made it difficult to work out what was required to unclip it.
The '89 GLT has a bracket and screw to the LH rear side of the radio. The Torslander's fascia panel was seperate from the radio, and only needed widening a few mm to fit over the new CD player.
The ISO looms are advertised as for non-amplified cars only. Perhaps not clear in the article, or maybe I'm just easily confused, is that the amp, complete with amp-radio loom can be removed from the car. The ISO lead then plugs into the main loom, just as with a non-amplified setup. My new CD player now works just fine, with only the white, 9-pin socket connected to the car.