I thought I'd pass along some useful tips on identifying rocker boxes. All have the 65-1506 casting number, but:
BB 3/8â€-20TPI acorn nut (65-0311). Also, has no threads in the casting for the rocker shaft
CB DB DBD 1/2â€-20TPI acorn nut (65-1856). Has Â½-20 threads in the casting for the rocker shaft.