Aaron, Delta 767's are configured 2-3-2 in coach. If there are two of you traveling, see if you can get a pair of exit row or bulkhead seats on either side, that's about as good as it's going to get in back. If you're tall, you'll want the aisle seat to avoid fuselage curvature (it's not that big a deal, but every bit helps). If you're not just tall but also a big guy, note that the exit row seats have fixed dividers between the seats, whereas in other rows you can put up the middle arm rest and slide around.

I've flown transatlantic a few dozen times on 767's, it was the only plane AA and UAL flew to London in the mid-90's, and Delta used to fly them to Prague (and still flies them all over Europe). They're fine planes, I never had a problem.