I used a 20mm hole saw to cut the holes in the bonnet for the locks to fit into
The lock itself is prevented from turning in the hole by have a square neck with rounded off corners. In order to mark out for the square section to be cut I placed the barrel in position and aligned strips of masking tape to the edge of the "flats" to transfer the square onto the bonnet.
I then used a small file to cut back the edges of the round hole to the edge of the masking tape to create the square hole.
Both locks fitted and the rest of the holes drilled and bolts fitted to the bonnet scoop.
Next job will be to cut the slots in the bulkhead which the bonnet locks slot into.