The ports flow better one the C8 and C9 heads. The closed chamber C3 head is restricted in port area, bur has a 52 cc chamber.The later heads come in at about 59 to 60 ccs. Once youve had it decked 40 thou and if you use a Victor Reinź composite gssket, you should gain more airflow with the 1.6 inch or grester log cross section from carb to valve.
The best option is the D8 head planed down, with a direct mount modification for a 2 bbl Holley or 1.33 Autolite.Stanyon and Crosley did an excellent write up with photos on each of theirs.