The only single row factory engines I've ever seen are 84 or newer I believe, nothing older. Dual row is the way to go, and I have a stock 81 w/350,000ish miles on stock everything to prove it. I'm real tempted to get a metal guide for my '91 for piece of mind, but it has around 35,000 miles on a toyota chain so I'm not too worried about it yet. And Kyle is basically right about the differences between the engines, there are no real block differences aside from bore, it's mostly up top. If I ever see a single row chain in an older rig I would assume it's a replacement.
