G'day Ross, recently been through this myself... I think what you're after is a 1500 beetle or type 3 box and do the straight axle conversion.
Two posts I started at the time which migth answer a few questions:
http://www.aussieveedubbers.com/forum/viewthread.php?tid=22152#pid173561
http://www.aussieveedubbers.com/forum/viewthread.php?tid=22769#pid172547
I ended up getting a box with modified axles fitted and adjustable front beam (no redux hubs lowers the back by 4 inches so front needs lowering too) from CBB in Penrith, had it shipped up here, and had my mechanics fit it. But they hadn't done it before and ended up taking a heap of time doing it and ran into a heap of problems (not to mention that the front beam that CBB sent up did not fit, so I had to send them both back and get adjusters fitted to mine).
So it cost me. If I had my time over again I would have shipped the car to CBB and had them do it all. The box and kit is great and CBB know how to do the job quickly and easily...
I'm told you could do it by yourself for under a grand. After all the stuffing around mine cost me $3k (including front beam)...
Hope that helps, good luck!