Batteries are grouped by a Group Number. Rootes used two different groups… a small Group 24 battery and a larger Group 27 battery. You can use the more common Group 24 battery in your Alpine, it just won’t start as well in very cold weather. In addition there are two versions of each Group battery… the regular kind and the "Ford" kind with reversed terminals. Check the orientation of the terminals on your battery. Usually on positive ground cars the type of battery required is a Ford type… either a Group 24-F or a Group 27-F.
Hope this isn’t way too late.