Here is the photo of looking up at the tunnel from under the vehicle.
The next step was to check the width of the engine mounts against width of the chassis...
Obviously...I should have know at this point...nothing was going to be easy...The chassis was too narrow for the original cast alloy engine mounts.
Only way to make it fit was to make up an engine mount to fit the chassis...
The way to do it was this:
Measure both left and right mount hole position in relation to the crank shaft centre line.
Work out the ratio between both measurements.
While maintaining the ratio between both measurements reduce the total distance until it fits inside the 600 mm width which was the distance between the chassis beams.
Here is what I made.