I'll actually be using the rockers and shafts from the '70 heads since they're in such good shape. As for gears, plans are to eventually go with 3.23's Rear is actually an 8.25 and yes it's original, believe it or not. I can't see compression being in the 7's, stock compression listed for a '70 teen is 8.8:1 in every piece of literature I've read. Might be down a bit but that much? Cylinder pressure is really good across the board.