Motorcycle sizes help please?

I am new to motorcycles and am wondering what size bike (specifically Harley Davidson) would be suitable for someone my size. I am 6'3" and weigh approx 340lbs. I'm looking to pick up a used bike because it'll be cheaper. The power of the bike doesn't concern me. A lot of advice I'm seeing states that new riders should start with a smaller bike. I don't want something that is going to be super uncomfortable or a bike that is waaaay to small for someone my size. Nor do I want a bike that will reach a top speed of a whopping 30mph trying desperately to haul 340lbs! I was thinking about the 1200 custom or the fat bob. Any advice would be much appreciated. Thanks!