Enh, I'm not really interested in Megadeth covering Led Zeppelin songs. Really, by definition you couldn't top what they already did.
Actually, now that I think about it, Achilles Last Stand wasn't heavy enough. Go record that, Dave!
He's like "yo give me yo insurance information!" and I'm like "I didn't hit you with no car, I hit you with this mack truck I call a fist!"