Hi, with the information above i can almost figure out what moter i have but not quite. I'v had this truckfor almost 3 years now and still do not know exactly what i have under the hood. The Stickers on the aircleaner and valve covers say that its a 406 but my cousin claims that its a 390. I looked at the casting numbers on the outside of the block and beside the oil filter it reads"6G15" and then on the other side of the block below the #1 cylinder it reads"C6ME-A." And from the chart above it would mean it is a 390 or a 428. So if any of you'll have any ideas on finding out what it is let me know. If need be I'll post pictures. Thanks!!