Applied in a very thin layer pure silicone grease or any non-migrating dielectric should be fine for this. Please keep in mind the least amount of grease you can apply to the distributor cam will be what you want. The cam will try to sling anything on it off in a centrifuge fashion, the points will naturally be constantly trying to wipe it off and you want your points to stay as dry as possible. Wheel bearing grease made specifically for disc brakes might be ok. Anything subject to migration under heated conditions won't be so good for you.
