Thanks for your reply. For your information, I was able to get in touch with Bill Wolferstan and he was able to solve some of the mystery surrounding lack of information on the Gulf Island 29. Bill thinks that only about 6 of them were built at Chine Boat Yards in Vancouver. He does not know at what stage of production they were sold but his had an external transom hung rudder wheras all the others were internal rudders. Bill and his wife Clementian enjoyed "great sailing in Tumbo for 25 years".
My boat also has one of the cabin berths converted into a dinette and I do intend to post some pictures if I ever get the process figured out.
I have a couple of the Wolferstan books, and have always liked the look of his boat with the externally hung rudder. Did he mention where Tumbo is now? If only 6 of these boats where made at Chine Boat Yards, were the rest sold as kits? I found some photos of your Wrinkles on-line and saw that it has two more windows than mine, and also a bigger engine (which I envy, I have a 13 hp Yanmar 2gm, a bit slow). Good Travels!