I think you're misunderstanding their importance. While it may be true that a c-clip axle's shaft may not immediately walk out after breaking if they are equipped with a disc brake conversion, that in no way means that it would be safe to drive it that way. Side loading of the axle shafts when on the road would overcome the caliper mounting bolts in short order, and could very likely rip the caliper from its mounts, letting the axle come loose from the housing at speed, and most likely causing a serious accident.
In other words, keep the c-clips in place, or use a set of c-clip eliminators, if they are even available for your axle.
C-clip rarely break on axles with a more robust housing design than a Dana 35. The main weakness of the 35 is a weak housing, which actually flexes quite a bit. In turn, that puts extra stresses on the carrier, and something has to give. In a 35, that's usually the c-clip end of the shaft if you're lucky, and carrier or spider gear breakage if you're not.
