I went and looked at one today and the actual lead with the RJ45 plug on the end cannot be changed like the other GME unit, but it should be able to be extended using an RJ45 jack and a short Ethernet patch lead.
The other positive is the face unit will fit perfectly up in the sunglass holder. Just needs two rivets into the plastic to hold the bracket, and a hole big enough to fit the RJ45 plug through. The only unknowns at this stage are how hard it will be to get the cable down past the curtain/pillar airbag and where to put the microphone clip, and where to fit an extension speaker as I'll hide the unit up under the dash somewhere.
Here is the unit for those who like pictures! They are actually discontinued so old stock is cheap, I have seen them for $400 or $470 with a $150 list price GME elevated feed antennae with spring base.
https://www.gme.net.au/catalogue/fixed- ... 3520s.aspx