If you can't get a plug you could also cut of the Ford's plug and wire the ISO-connector that is coming with the Mk2 to your car's cables. (Some good aftermarket car radio installers can do that without any problems). The only thing about this is that you don't have the original Ford plugs if you sell your car. But who cares? (nearly) all aftermarket stereos have ISO-connectors.

I'd seriously think about removing the factory installed radio and installing the Mk2 instead.

TeeMcBee