The idea of taking the dimensions of your existing bike and finding a new one with the same dimensions makes sense.
If you can find a Look dealer, I'm pretty sure all Look models are available as frames only. I don't know how the racier ones feel, but I absolutely love my 566. It feels like it wants to go fast, so I find myself riding much longer and harder that I otherwise would, yet it's extremely comfortable over our cracked and broken roads.