We extend to you a cordial "WELCOME ABOARD !" Come on in, make yourself at home, we are a friendly group of enthusiasts, and we also appreciate the classic Chris Craft Roamer, Corsair, and Lancer boats too , as they are all on the same family tree and share much in common ! Just start by posting a note introducing yourself to the group, that's all it takes here (we don't ask for or retain any personal information here, because our intention is to just "have fun and share information".
Thank you very much for posting those photos. As Paul said, your boat is definitely not a '68. Most likely a '63 or '64 but I'm leaning toward '64 because the motor number is about 200 higher than the other '64 boat I've been looking at.
Your motor number decodes as:
G = 2bbl carb with aluminum intake manifold
R = 221 Ford Interceptor (140hp)
90 = Eaton I/O outdrive. model B
R = Right Hand rotation (as viewed from behind the flywheel)
319258 = the numerical serial number of the motor
Those Ford blocks have a casting number on the side of the block which will identify the year.
I was surprised to see the Thompson & CC logos applied to planks under the deck. These SeaV-20 boats went through a lot of small variations through '63 & '64. Such as port helm vs starboard helm, vinyl covered helm box vs varnished wood, air intake and exhaust scoops for the motor box that faced opposite directions, Thompson logo on the stern vs Chris Craft logo on the stern, a motor box with two small seats on the sides vs a raised full width bench seat.
Good luck with your boat. It's a rare piece and deserves to be preserved well.