Jack,
Here’s some more info:
According to the 6CAR War Diary:
https://heritage.canadiana.ca/view/o...57/117?r=1&s=3
The regiment moved from Lee-on-Solent to Fort Monckton on 19 May. If this image was taken at Lee-on-Solent then it should pre-date 19 May.
The diary also mentions that the loads were marshalled on 2 June.
Much of late-May was spent waterproofing and modifying vehicles, so it certainly is possible that the tracks were changed after this image was reportedly taken.
To me it seems odd that the landing craft serial would be chalked on the vehicle possibly 2 weeks prior to marshalling for the load, but I have not attempted to research this type of question before.