BulletProofDiesel reminded us that the '03 6.0L Power Stroke has a round-style EGR cooler, and '05-and-newer engines came with a square style. Most '04 models have the square cooler (right), but early '04 models have the round version (left). You can tell by the VIN number. A sample VIN number is: 1FTRW21P24EB10150. In the middle of the VIN number, you see the digits 4EB. The 4 means it was an '04 model year. The E denotes which production plant built the truck (in this case, E is for Kentucky). Lastly, the B is the start of the sequence number (the last 6 digits of the VIN). Some early '04 models have a 4EA code. The A denotes the early build and most likely is a round-style cooler. The B, C, D or more all denote later-model '04 builds with square-style EGR coolers. Round and square models are not interchangeable.