Holy Crap! It took me forever to find the stamp! It's exactly where it was supposed to be, right where I was looking under paint and goo and crap. With a little help from photoshop, here's a pic, just so I'm sure.
Now, from what I've gathered, the 6 digit code is supposed to be the last 6 numbers of your VIN, which doesn't match mine, and I don't really care since I'm doing cool custom stuff anyway. The letters, however, are YB and if I'm looking at everything right, it seems that it's a 400. The hood then is probably the original, and the original engine was most likely the 326.
