I will answer that.
What you are seeing in the photo that may seem to be a slotted hole is, in fact, a second set of holes. There is plenty of metal between the two sets of holes, don't worry.
The rearmost holes are used in the case of the earlier models of Morgan that have part of the handbrake mechanism on the back of the diff. In that case the axle has to be mounted aproximately 20mm (3/4") further forward to avoid impact of the mechanism on the fuel tank. This would be the same position as with the leaf springs. Taking accurate measurements before you start is part of the installation proceedure.
The car in the photo is a relatively late model car that uses a cable machanism and the axle can be mounted in the rearward position. This centres the wheel better in the wheel arch which is more aesthetically pleasing.
There is also another variation which can be ordered. This has a narrower cross bar for the older narrow chassis cars.
Last edited by Gambalunga; 12/03/16 09:56 PM.