People know Tet occurred around Christmastime and in 1968 (of course, it was near the Xmas of '67). Could that be where the mistake came in?
Could this be a Kerry op designed to smear anti-Kerry veterans by getting them to associate with a fraud, which would then be revealed at a more opportune time? I'd just stick with the established SwiftVets.com. That group was smart to only accept Swift Boat veterans (people they know).
You may be right about a typo which should have read 1967. That would cover Tet in early 1968.