Having just done up a customer's MK3 gearbox with a reverse camplate, I can attest there is no difference in camplates from MK3s to other year Commandos, other than the aforementioned rivet to trigger the neutral indicator light, which I had to move. Since the camplate is hardened, drilling for this rivet had to be done properly (some even recommended Spark Erosion). I did it on the Bridgeport with a proper bit and it worked a charm.
Ironically, I had to install the reverse camplate to keep the One Down/Three Up shift pattern that is stock on a MK3 as this customer is using rearsets and thus removing the gear from the primary which switches the "GP" shift to "street" shift in the first place.... so, a lot of work to get something back they way it was, all in the name of esthetics!