The economy rows in the picture on seat guru do not appear to line up with each other. For example do 60G and 60H line up next to each other. I want two aisle seats that are directly across from each other.
Here is the official Cathay Pacific seating map (pick 77H from the dropdown, there are multiple different models). As you can see, seats do not line up across the aisles, although the gap is slightly less pronounced towards the front of the each economy cabin section (near rows 40 and 60).
I want two aisle seats that are directly across from each other.
As you can see in that seat map of the triple seven 300 77H:
every pair or rows doesn't directly line up to each other.
If you interested in an approximation, then I'd suggest you to check the rows 68-72, which are located towards the tail of the aircraft. Personally, I would go for 69, if I was you.
At that section, the cabin gets narrower, thus the distance between the rows is smaller (which might be a good thing, if for example you intend talking to the person at the other side), in respect to the distance between the rows closer to the center.