If you pick up a used cylinder it
should be fitted. However, there is a slim chance that it might just drop in- I got lucky.
The only way to obtain an extra cylinder for a gun that did not come with one is to buy a cylinder used or have one made by someone- Ruger has a very obnoxious and draconian parts department bureaucracy, and will under no circumstances sell one, nor fit one to a gun that did not come with it.
On the issue of the new, smaller frames- not all Blackhawks are on the smaller frame. Deandog has some pictures of some distributor exclusives in the two stainless Blackhawks, one of which is a Bisley (very, very nice I might add
) .
I don't believe that any of the Blackhawks (including the new flattop frames) are on the smaller frame of the new vaquero, but I could be wrong.
I tried to google a picture of that pin on the frame and I cannot find one.
Don't discount the Bisley if you are going to be throwing some fairly hot loads, as it may offer better control for you under heavy recoil- at least feel of one.