disk brake kit

Dr. Diff sells a disk brake kit that accommodates the 14" steel wheels and I would put money on it that you could ask him to drill the rotors for sbp.

If that won't work, Scarebird sells a disk brake caliper adapters that work with the drum spindles. You can either buy their entire kit or just the brackets and source the calipers, rotors, etc yourself. AND! Their kit works with 14" ralleye wheels. I have this kit on my Dart right now. If you go this route, be careful, because they sell kits and brackets for 9" & 10" drum setups.