There never was a cast iron 904. First year for the 904 was 1960 and it was for a slant six only. First V8 904 was 1964, when the 273 was first introduced.
BTW, I had to grind on the 383 block in my 64 Polara when I put a lightweight starter on it. Can't remember what the interference was, but I think it was the factory adapter on the two electrical terminals.