OK, according to the sticker on the door jam, the truck was built in Jan 1971. The stamped number on the block indicates the engine was assembled on December 23rd and the suffix code indicates it is a 1971 402 for a Truck. I cannot find the stamping that would have the production number, it is missing from the position on the front of the passenger head that the site I was looking at refers to. There is another place to look according to the site near the oil filter, so I'll try to find it tomorrow. My thinking is that it would be very difficult to have an engine assembled in December on a truck assembled in January and it not be the original engine, but I won't stop until I have definitive proof.
Any other ideas on how to find this?
Thanks,
Dan
