If the title lists it as a 1967, I would be inclined to assume that it is a 1967. Is the shop owner still available to ask him what it is that tells him it is older than 67? It would not be impossible to have the wrong year on the title, but unless there was some clear indication that it was wrong, it would most likely be a 67.
Because it is a rebuilt 1967 engine (that must be stamped on it?), it may be the original engine. The frame may have the serial number stamped on it, often located on the front left side. It should match the number on the ID plate, and match the engine number if it is the original.
It is not common to change the radiator when an engine is rebuilt, but it could have been changed at some point.
