This is my limited experience....
I'm not sure if OCR 3 is "integrated" or "internal"
the higher end Giant TCR frames are all 1 and 1/8 internal... with stock FSA headsets that could be replaced...
becareful about the 1 inch integrated... as far as I know... to get a new headset from FSA, Chris King.. you'll need one that is 1 and 1/8.
good luck