I think sailboat data just misslabeled the keel as fin instead of full, or 3/4s. Comparing the pictures in the two ads Island 29
, Gulf Island 29
it looks like the one labeled gulf has a more squared off roof at the front of the cabin similar to what I can make out on the front of the boat in the picture near the beginning of this post.
I'm waiting to hear back from the seller but do you know off hand what the LWL is and how much ballast the Gulf carries?