Just got back from aformentioned SI trip.
Calculating the direct route (sans all the other driving we did) that's 1,900kms. Not bad for a fully laden 1980's wagon. We did need a $700 brake job in Dunedin, but apart from that (and 4L of oil) she ran like a charm. If you're reaing this Alex, sorry we didn't make it your way - will be back down again sometime as we want to do some wine tours, so will hook-up then fo sho!