The baseplate off a 4223 850 center squirter works but it would be next to impossible to find two of them. Even if a person could come up with two, it would be a crime to rob parts from them. They belong in a glass case for bench racing purposes or maybe on some sort of nostalga car, not pirated. I have seen in print where a baseplate for a 4781-2 can be used with a 20-3 1:1 conversion kit. The only baseplates Holley shows for the 4781 series carbs is for the 4781-5,6,7, or 8. Personally I'm going to call up one of the many carb shops and buy a set of billet plates, with the buttonhead screws and thinned shafts. Most of them have done this before, and will know what works.