I found this today while looking for info on different sizes of different front forks.
It may be posted already, but it may not. so it may be helpful
here's the Tube sizes... its the OD of the tube, wish it had length and axle OD as well...
http://www.ohiocaferacers.com/OCRTubeSizes.pdf
and the clamp sizes
http://www.ohiocaferacers.com/OCRStemSizes.pdf
Im fuzzy on these clamp sizes as to what they mean...