I don’t think they are CMP wheels. I’m far from an expert on the CMP, but all photos I found of them with a short search show wheels without those eight holes in them, the tyres look too wide and fat to me and the pattern is clearly not an all-terrain type like you usually see on CMP trucks.
This vehicle also seems to be very short-nosed for a simple body transplant from a Rolls-Royce armoured car. I get the impression the nose was cut off just in front of the forward engine cover catch and the front plate then re-fitted to the armour. Though having said that, I find photos showing different locations for those catches:
… so maybe the nose wasn’t shortened after all? Though it still looks shorter than on the two above.