I went into the inner sanctum and checked Michigan Wheel Catalogs 1939 1950 1954 1956 1958 1960 1962 1964 and could not find J278 . Can anyone shed some light to what the prop goes too?
It doesn’t turn up in my ’49 cat either, but the other J27x seem to fit an SD. Sometimes Michigan used adjacent numbers for a bronze and an aluminum prop with the same specs, but apparently not here..