The basic 130-tooth flywheel didn't change from '62 until the end of production, even the same casting number and they were used on both BB and SB.

External balancing was usually done by drilling a hole or holes of a certain diameter and depth; some external balance drilling is easy to spot but some, like the 340, is so small it can be confused with mass balancing drilling. In that case it helps to know the location of the external balance drilling in reference to the crankshaft bolt hole positions.

Best to post pics of the flywheels in question.