They wouldn't be a pure 3 way cross. No such thing can exist. If you built a family with that blend it would be your dogs. Examples Mims, Boyles, Busenbark, Garner, Vise Grip, etc. All have blends but they become one behind the breeders efforts. Or, you can take that one crossed dog from the blend and commit to line breeding and inbreeding on it. I.E. Frisco, Mayday, jeep, red baby, etc. Nothing is pure just the efforts to focus and cultivate.