Yes tomturney, it sounds like you have the 2012 (older) style stem. All of the 2013 Scalpels that we've seen at my LBS did too. My stem was ordered separately and did not come on a complete bike.
Remember, when you compare the older stems, to the OPI stems, you must include the weight of the steerer tube into the equation.
As I mentioned above, the total weight of the newest (2013) 110mm/-5 degree OPI stem/steerer/spacers is 293 grams.
I have a 2006ish Cannondale stem that is 120mm long/+or-5 degree rise. It weighs 203 grams with steel steerer bolts and faceplate bolts. You must add in the weight of a steerer tube to go with it to be comparable to a OPI stem/steerer/spacer set-up. Now, the total weight depends on which steerer tube you use. I have an older Lefty steerer that is mostly straight and has no cut outs. It weighs about 134 grams. Add that too the 203 gram stem and you end up with a total weight of 337 grams. I also used to own a Lefty steerer that was a bit lighter. It was tapered down more in it's middle section and had a large hole cut out of it near where the stem attached. I sold it, but if I remember correctly it weighed about 110 grams. Add it to the 203 gram stem and you would have 313 grams.
Keep in mind I'm not exactly comparing apples to apples here, because my newest stem is only 110mm long, as where my older stem was a 120mm.
My best guess is Cannondale changed to the OPI set-up from the type that could house the tools, to save weight. With that said, the 2012 OPI style is probably a bit lighter than my new 2013 model because it does not contain the 4 internal spacers.
Our best guess for the current revision (with the 4 internal spacers) is to eliminate that awful creaking sound that so many have complained about. This latest version should eliminate that, and still be a bit lighter than the older setup where the stem bolted on (and could house tools). I have yet to finish building my bike, so I can not confirm if the creaking issues are resolved. I should have the thing wrapped up soon. I am still waiting on Mavic to cough up a XD Driver freehub body for SRAM XX1 and I'm waiting on my Magura MT8 brakes.
I am not aware of any reason that would prevent you from running your old stem/steerer on your new bike. I think it should work just fine.
I hope I answered your questions.