Hi Remi, welcome to rollaclub. Always good to see old rollas getting round in other countries! :lolcry:
You could find the parts you are after for sale here in Aus, but postage would be very expensive, maybe not so much for the springs but deffinately the gear box.
The only difference between a ke30-55 gear box, and a ke70 one is the shifter position. The ke70 one is 10cm/3" or so further back, so putting one in a ke30-55 requires cutting the transmission tunnel for the shifter to come through.
To you have any kp61 starlets in Norway? They also have 4k motors like ke30-55 corolla. The Starlets also come with 5 speeds, so if they are more common than corollas you might be able to find a gear box for them. :y: Depending on what model it is you might have the same issue with the shifter position.
As for springs, find out how much these companies could post them to you.
http://www.pedders.com.au/contact Have a look in catalogue for ke36-38
http://www.kingsprings.com/
http://www.lovells.com.au/products.php?p=coil