Ken, the company you are speaking of was probably Cordell.
It is believed they built 3 such cars, some say more. Some also say that GMH were involved, but I don't think that is the case.
The most well known example today was in the Hughes Bros collection and also appeared at Holden's 50th anniversary celebrations at Fishermans Bend.
I have also heard and seen pics of another that was pulled out of a shed with major roof damage a few years ago.
It may well be this car.
The grey car pictured at the AHD is probably the cordell clone that was produced by Phil Munday.
The story goes that he was restoring an original Cordell built car (probably the one directly above) and had to have his own.
He set about building it using the Cordell built car as a guide.
Whilst we are talking FJ wagons. here are a couple of pics of the GMH built prototype.
As you can see, completely different styling.
Regards
Alex