How do you tell the difference just looking at them? I have what I think is a 2.25L 5 bearing engine but it has the Weber carb that the 2.5 came with stock. I'm assuming this was added later, but I have no history on the truck. It has a later style Ducellier distributor, not sure if I can draw from that or not being a trait of one or the other. I'm pretty sure the serial number matches up to a very late 2.25, but who knows.