IMO rider height is an inadequate dimension to use to determine frame size. Back in the day (think Greg LeMond era) one method of sizing was to take .667 x inseam for a measurement. In your case that would be a 49. However, there are three traditional fits......Race, French and Eddie. They usually give a range of sizes that can be used. In my case 54-58. Different stem lengths required for proper fit. With the advent of sloping TT a sizing tool called "stack and reach" is being used by most fitters. I have come to believe that knowing your proper TT length (on sloping TT, "virtual" length) is a pretty good determinant. My 58 Masi and my 55 Guru are equally comfortable and efficient once the proper stem size/angle is thrown into the mix. Were I buying a bike from a shop I'd go to one that knows how to fit me and includes a fit in the price of the bike.