Well, not many images of the 351M/400M motors as they aren't all that popular but they do indeed look like a Cleveland but with more emissions junk on them due to their date of manufacture. I'm not positive but I don't believe that Ford put a single 351 Cleveland in a truck at the factory. If it's original and it looks like a 351C in your truck, chances are that it's a 351M. The 400's found their way into a lot of station wagons and heavier cars.