Canadian Chevrolet Maple Leaf 4x4 artillery tractors?

[nuyt]

The picture of the Art. parade with the horseback staff watching is interesting:
I think it shows the Morris-Commercial artillery tractors (to be superseded by the GMC´s) AND GMC´s munitions trucks simultaneously.
It must be around the time the GMC´s were introduced, but not fully incorporated.
The next picture is a GMC bodied as ammo truck, I think. Next to it is a Chevrolet staff car of the earlier typ (late 20´s and similar to the Signal Corps truck), but still going strong during and after WW2 (see my other posting-Chevrolet ID help needed).
There´s also a picture (I will look it up bavk home) that shows the heavy AA guns towed by other trucks, possibly the GMCs.
Greetings
Nuyt