Steve, that will be the Mildren car. It must have been converted sometime in late 1966. KB is shown running it in LHD form at the July 17, 1966 Warwick Farm meeting report in 9/66 Racing Car News.
I can't see any listing of the GTA in the September 18, 1966 WF meeting. But KB was entered in something even more exotic that meeting - Mildren's TZ2.
In the December 4, 1966 Warwick Farm programme the car is entered with both Gardner and KB down as possible driver. That should be the meeting that photo was taken, as the 1/67 RCN report mentions Gardner as the driver.

Stephen