I have a 1963 Breda shotgun as well. Very well built guns, can be taken apart without any tools, the long recoil is very nice to shoot, and it looks a lot better than an A5. They were more expensive than A5s when they were released to the North American market and therefore never really sold well. The safety can be swapped to either side, it has a mag lock-out, and the chokes are expensive so if you find some, buy them and hold on to them. I have a manual and I believe I found a digital manual online somewhere. As for steel - though the barrel was not designed in these days for steel, it is quite a thick barrel. I would say use steel at your own risk but I will be using steel through mine.
Here's the manual: http://stevespages.com/pdf/breda_12.pdf