At 6' 4", I find that 62cm production bikes fit me. Have you not found this to be true? Do you find that stand over or top tube are harder to find in adequate size?
Not all manufacturers produce bikes this big. I would recommend you take a look at Surly. The LHT would be a capable rando (and if you really need it, has a 64cm size available soon/now). I understand people use the Cross Check as well. They are generally recommend for rear biased loading, which might be a strike against them given your stated preference for a front loader. Two other production frames that come to mind:
SOMA San Marcos (a listed 63cm frame) and the
Black Mountain Cycles Road (the designer is tall himself).
I own an 1980 Fuji that fits well with a moderate stem and a fist full of seat post (about 60cm top tube, I forget the seat tube size). My 62cm Surly Steamroller (single speed) has a 61cm top tube and also fits great.
As seat_boy pointed out, the Oceanair might be a good choice when it comes out. I too am watching that development.