I went to a motorbike wreckers and bought a doodad that fits on the end of a single cable and enables you to join two cables on to it. So you end up with a "Y shaped" cable - single at the knob end and double at the carbie(s). I seem to recall paying about $25 for the doodad and two shortish cables that came out the carbie end. You can use a standard datsun single cable inside the cabin and it will look right.
63A box - ticks all the boxes! Hard to find but worth the effort as it's all a bolt in fix. Should be strong enough to cope with a turbo (and these are the key words for any transmission) if used with some care.