Gordon Yeo made up a couple of gas tanks. They did look good although a few minor details didn't match originals. I would much rather live with minor details being "off" than have no tanks at all.
http://www.mapleleafup.net/forums/sh...ighlight=tanks
If you don't 100% trust your welding of the tank joints, use tank sealer to correct any minor imperfections. It is claimed safe for sealing pinholes so should cover similar size manufacturing lapses. Lead solder is another sealing option - the heat involved is safe since there's been no fuel in the tanks so far.
A filler neck that might be usable (with modification) is at
https://www.macsautoparts.com/early_...ck-375225.html
Tanks Inc sell a variety of fuel tank parts in addition to complete tanks. Sender flanges to stiffen the tank at the sender (either Ford or Chev pattern), filler necks, T-bolts for making replacement hold-down straps, pickup tubes (although it looks as if they are easy to make)
http://www.tanksinc.com/index.cfm
They do have an Australian agent although they look to be on the other side of the country from you.