The left hand Engine Steady for the '71 to '73 Export Moke is different from all other models to make way for the fitting of the Master cylinders on the left. This article shows how to modify, shorten, a standard the engine steady to suit a mismatch of the engine and firewall brackets.
There are three components to the left side engine steady arrangement on the Export 1275 that are unique to that model to account for the likelihood of the car becoming a left hand drive vehicle. The bracket that mounts on the firewall moves over to the right of the base, the engine steady is a longer straighter item and the bracket on the engine/thermostat is unique for the Export as seen in the image below.
I had to repair a Moke that had the standard bracket on the firewall and the original Export bracket on the engine meaning neither the original engine steady or the standard steady were going to fit. 
If you compare the firewall bracket in the above pictures with the same bracket from the original set up you can see how it is offset to the right of the 'heater hose' holes.
The solution was to shorten a standard engine steady by 50mm however you will need to verify this with your own set up as there are at least two brackets available for the firewall mount. In this example the bracket had two holes and I shortened the engine steady to fit the closest hole.
The most difficult bit of the operation was trying to hold the two pieces together straight enough to weld them as the castings is rough and nothing wanted to sit flat or straight. I did a straight cut and then bevelled the ends to give the weld a V to sit in and it didn't come up to bad after a cleanup on the grinder.
The alternative to doing this modification would be to find a 1275 engine bracket and convert the whole set up to a standard 1275 set up.