I did a rough calc and figure a 64 to 66 cm bike should fit, based on the standover you gave (it's a rough guide). Top tube length makes a difference too - you might be on a bike that's too short or the stem is too short and you feel like it's too small when it's really not long enough. Keep in mind that many older factory frames were made with short top tubes. For example I have a 62cm frame I can ride only because it has a 56 cm top tube, even though it has a 34.5 inch standover and I've got clearance for 35 with shoes on (I'm 6' 0). My best fitting frame is a 58 with a 57 TT.

cyclotoine's recommendation for using a longer crank is a good one. A longer crank also also helps to lower the seat height, which puts the seat and bars closer to the same height. I like 175mm and can only imagine that someone 6'3" would like 180mm cranks.

This guy is also really tall, and has a bit to say about it:
http://www.zinncycles.com/cranks.aspx

What size bike are you on now, and what sizes have you tried?