For what you say you want to do, I would suggest that stack is as or even more important than reach. For long miles you'd want a more upright position and that is really hard to obtain for tall riders. Look at bikes with a really tall headtube. Most bike makers use standard forks that only come with 300mm steerer tubes, and so don't do really long head tubes on their frames. Note the height difference for headtubes vs seat tubes from small sizes to the largest ones. They don't both get longer at the same rate! A 747 may actually be a better fit for you due to the tall head tube.
I'm a measly 6'5" but all legs and arms too. I just went for a Canyon XXXL CF SL. It's fantastic with it's taller headtube, but I'm still a shorter distance racer with a heavy leaning towards track racing, so my geometry needs are very different from yours.