You will need to change the diff shafts if you want to change to pot joints or hardy spicer. This means taking the engine out and removing the diff housing to get to diff itself which needs to be pulled apart. If you do go that way, you can remove the swap the outer cv joints so you end up with your pot joint shaft with a drum brake cv joint.
The easiest thing for you to do would be to find some QL5000 (pretty sure that's the part number) which are a direct replacement for the rubber uni.
http://www.minispares.com/product/classic/QL5000.aspx but finding some may be difficult, i just searched a couple of the aussie suppliers and they don't have them stocked at the moment by the looks of things.