I have some advice on the printed circuit board, but let me first make an observation. As an aerospace engineer on my second Skymaster, I have been following this thread with considerable interest because of its insightful content. Especially the two comments from Kevin: first, that the original warning lights are too important to discard, and second, his theme (to which I'll add a little spin) that the electrical system is too complex and too weak for us to be modifying it.
My main suggestion to Peter is that the printed circuit board and other components which you are seeking might be found in good condition -- and at huge savings -- from parted-out Skymasters which spent most of their life in arid regions. The "Purchasing Parts" page of my Skymaster website at
www.SkymasterUS.com gives detailed directions on buying used parts successfully and provides the names and contact info of suppliers. I would start with Don Nieser at Commodore.
Also, to make sure that you have the right part numbers, you may need the aircraft serial number; this is particularly true if yours is a French-built Skymaster. Finally, the optimum approach is for you (not someone else) to look at the Illustrated Parts Catalog, so that you can choose from the illustration all of the parts you need and their part numbers, and to make sure that those part numbers apply to your aircraft serial number.
Ernie