When I put mine back in I cut off some of the iso connectors and soldered the cables together to allow it to all go back in no way would it all go back in with out doing this with the extra adapters
It is possible to get it all in place, just a bit of a nightmare. Mine has a proprietary connector that then provides ISO plugs on flying leads. Those then connect to another ISO lead for my Parrot phone kit (to route audio through the speakers) before finally connecting to the car's loom. I have three pairs of phono leads coming off, a little box of tricks for the steering wheel interface, and a DC-DC converter for the head unit's power supply.
So there's a lot of stuff in there, and it's not fun getting it all to fit, but I managed it. Admittedly I did have to remove the dash panel to find all the little nooks & crannies that I could stash the various connectors so there'd be room left to push the head unit in :O.