I bought a 56 C600 coe and I thought it had the original motor in it but now I`m not so sure. The  truck has a 4bolt 2bbl manifold on it, and a Stromberg 2bbl carb from a 60s mopar on it. I had a 56 F600 and I remember it having a Ford/holley on it with the 3 bolt flange. Question is what is the manifold from? Casting number is ECR-A, can`t find the date code. I`m thinking it might be a Merc, but I`m finding traces of the original yellow engine paint on it. Any ideas, as I`m thinking it could have been swaped out and the motor may be the stocker.