THe first thing you need to do is join the Grand Banks owners association, IAGBO (International Association of Grand Banks Owners) Grand Banks Owner's Resources
Any questions you have about any GB product will get answers from people who have been using, working on, repairing, restoring, upgrading--- you name it--- these boats for decades. There are people on that forum who have 47s and 49s as well as every other model.
Bob Lowe (one of the founders of the forum) is particularly knowledgeable about GBs because for years he owned and operated Oak Harbor Boatworks, one of the country's premier yards for doing virtually everything that needs to be done on both wood and fiberglass GBs.
There is also another GB owners forum administered by Grand Banks themselves. GB Beacon | Home for Grand Banks enthusiasts across the globe
You want the "Discussion Forums." This forum is not as active as the IAGBO but they have a resident expert, Mike Negley, who is as knowledgeable and experienced as Bob.m So it may pay to join both of them. But for sure join the IAGBO. It's the best GB resource on the planet.