The 2.25P in the army series 3 was esssentially the civilian engine with the double pulley and fan as you said.

The Australian army series 3 fleet only had the 2.6p six cylinder engine fitted.

The front exhaust modification was for workshop and radio vehicles only to keep fumes away from the operators at the rear of the vehicle.

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1981, Series 3 FFR. 33-727 - Grover
1961, Series 2 Ambulance. 108-098 - Eden

Registry of Ex Military Land Rovers Mem. 129
Defence Transport Heritage Tasmania Mem. 12

You know, strictly speaking, throttling the staff is my job