The old Citadel gangsters are very small in comparison to any gangster range available now - I think I would classify them as really "20mm" rather than even "old 25mm". I would have a look at the 1/72 Redbox plastic gangsters to see if they are compatible. The Steve Barber gangsters are the smallest of the current lead crop, and while I haven't eyeballed the Steve Barber figures again old Citadel for many years, I think you'll find that even they are not compatible!