Have you had a look at EBay? There are a few Z31's there, including this Californian, which looks mint. Click!
Wow that is a nice one, unforunataly in vic and an auto. I did go and have a look at that other z31 though. Couldn't take it for a drive though as has no rego and brakes didn't work. Also had a look at a Z32, but they look like they would just be to hard to work on and it has less interior room than the Z31 (I'm a tall guy). I'll keep looking.
The VG30ET (that is, SOHC per bank and turbo) was standard from 1986 in Australia. If this is an '84 the standard Aus market engine was the VG30E (that is, SOHC per bank and NA). If this is a Jap import, it may NOT have had an engine swap, but these are rare here. The VG30DE was only used in the 300ZR, 1988-89 domestic market.