No direct connection between Yamaha and Gracy is written or talked about here atleast to my knowledge. Yamaha bought (merged) with a similar, small drum company called Nikkan Drum Corp. and that became Yamaha Drum Co. around 67. Alot of the pre-Yamaha Nikkan are circulating on auctions here- I have a few at this time.
Gracy it seems was indeed a separate company from Pearl but at some point was purchased or merged into Pearl by 1970 or so it seems.
I currently have a 3-piece set of Gracy drums in a nice blue sparkle with alot of signs of not being a Pearl made kit- different lugs, tom mount and badges that say "Gracy Drum Manufacturing Corp." I don`t have the kit assembled currently- some of the lugs are broken - I`m contemplating just selling it as shells with badges for a re-builder. I`ll take some pics