Agree on the Co-Mo Periscope 700c model, but at 6'4" it may be at the max height limit for the pilot. Would suggest leaving steerer tube uncut, for max handlebar height (use lots of spacers!); also getting the max-adjust *pilot* stem for a bit more upper body 'reach.' A bit over $3,000 for a new one.
Good luck.
Pedal on TWOgether!
Rudy and Kay/zonatandem