No pictures?
An Atala is almost certainly Italian thread. Do you still have the BB cups? If so, you may as well use them (unless they're hopelessly thrashed) and just get the proper spindle to mount whatever crank you eventually use. Be aware that the fixed cups are often installed
very tight; I was unable to remove the fixed cup on my Atala Grand Prix even using Sheldon's tool. I took it to the local pro shop (it was the first time in over 30 years I had taken one of my bike to a shop for service -- I do all my own work). The worked on it for several days using heat, cold big wrenches and so on, and also failed to remove it (I did make sure they knew it was Italian thread so they would be sure to loosen in the proper direction). Eventually I was able to remove it using Hugh Enox's universal fixed cup tool, but until then I just used to old cups.