I was recently in 68K (so I think the same probably applies for 68A, as well as 81A and K) which was marvellous - rows 67 and 80 have the A/K seat missing, so there is a massive gap to the row behind. Legroom aplenty, and the window too (although from 68, the curve of the wing rather takes up the entire view)!

It was also slightly further away from the lavatories, so if anyone was waiting, they weren't hanging around right in front of you. I don't know if these are available for pre-selection, but I think as the agent had to call to release the seats they are probably only available at check-in.