I assume he is using the term '59-style' somewhat loosely. The 5 in 59 means 1945, further meaning 45-48 engines. Sometimes there is debate on this, but generally 59 engines have 3-3/16 bore, and not 3-1/16. As a general comment, the 3-1/16 means it is Ford (not Merc), and pre-war. (Pre-war Merc's also have 3-3/16)