The C6's in 4x4 trucks had a deeper pan and, therefore, a need to pull the fluid from the bottom of that pan. To do that
And, here's the part number - D3TZ 7A102-C. I've added a note in my catalog saying that I think this applies not only to the E150/350 and U150 4wd's, but also to the F150/350 4wd's. In fact, I wasn't aware that the E's came with 4wd, as the listing for C6 pans shows, below. So, I believe the "E" for the E150/350 should actually have been "F".