Left hand fork slider

The 1972 parts book lists part number 060351 for the drum fork slider, and part number 063318 for the disk slider. What is the difference between the these sliders? They appear identical. Are they interchangeable? Note the caliper bolts on the right slider in this year. It was only later on that the caliper mounted on the left slider, so it is not a case of early vs late disk sliders.
Thanks.
Stephen Hill
Victoria, BC

When were Commando forks sliders strengthened, and made oval ?
The change from drum brake to disc brake, or earlier ??

corect disc brake set are oval.
Al