Hi Cliff
Only the No.1 ( I think it is) with the wooden body should have the split rims (10.50X20) not 18"
The "Trucks, 3-ton, Tipping, 2 1/2 cub. yds. (Aust) No.3" has 7.25X20 with duals on the rear.
So by the look of the tray on the upper one I think this is a No.3 as well.
Here's a Chev version of the No.3 with the wrong wheels
And another, also with 20" wheels:
