My 1925 Canopy Express uses a 366 P distributor too. When I restored it in the '80's, I was faced with the self-destruction of the pot metal housing. I fabricated a replacement housing and used the old internal parts. It works alright. But, from what I have learned since, a 374A steel housing from 1926-'27 can be substituted with modifications, like use the old internal parts and data plate (who will ever see it anyhow). If you are lacking the internal parts, I can probably dig up enough to make one up. Let me know if I can help at: gdchildsjr@sbcglobal.net
Good luck, George