There has been a Swift boats veterans' association (I don't know its official name.) for years but that's not the same as the SBVfT 527 organization.
I'll try to find their incorporation date or the date they registered as a 527.
Yes, there is certainly a distinction between the vet organization and the 527. From pages 4 and 5 in "Unfit to Command" which I am currently reading, a description is given of the SwiftBoat Vet reunions in Norfolk, VA Summer 2003.
That day Dan Daly, the master of ceremonies introduced many dignitaries in attendence and when the time came to introduce Kerry, Daly said "...who many be the next president of the United States. A deafening silence ensued. Daly was embarrassed and said "I guess I laid an egg with that one".
A year later another Swiftee gathering occured led by Rear Admiral Roy Hoffman, when the Swiftees had written an open letter to Kerry. This was right before the press conference they held in May 2004. Kerry accepted the nomination in what, July?