The date code on the parts is only part of the story. All the part date codes must pre date the engine assembly date code to be original as built parts. There is also a time lag between when the engine was built and the time it gets installed into a Tiger body. There was a lot of shipping and handling between the Cleaveland Foundry and the Jensen Plant.
My 260 engine was assembled in Jan 1965. The build date for my Tiger is Aug 1965.
I have an Original Tiger Engine Study Sheet for anyone who wants to know more about their Ford engine.