When I replaced my
axle two main things caused me to go with the original leading arm configuration.
On a
scamp 13 the axle is tucked into the right angle of the frame where the dining table floor rises (sometimes called the dance floor). Thus axle is anchored by welds along the vertical part of the frame and the horizontal part of the frame. Not just the horizontal part of the frame.
One of the advantages of a torsion axle is that it provides frame strength, it is a structural part of the frame. As opposed to a leaf spring axle that is detached from the frame and adds no structural strength. Removing a structural frame member from across the rear and moving it to the front seemed a more complex undertaking to do and maintain frame integrity.
That is not to say many people have not done it successfully, the shop I was at simply convinced me that "re-engineering" was probably less sound than replacement as originally designed. Pretty easy to convince me as I'm inclined that direction anyway. Heck it worked for the last 35 years why change it?
+1 on if it was ordered with specs for leading arm then installing it with that orientation is the way to go.