Externally balanced engine....TQ Converter Q?

external balance the crank is cast, damper has offset to it... then either the flexplate or torque converter has offset (not both)
so you use aftermarket neutral converter with aftermarket offset flexplate (b&m)

or

you use stock torque converter (has weights) and the stock neutral flexplate

you can get an after market neutral torque converter and mount weights on it if you can find someone that has that kind of knowhow. that allows you to use the stock flexplate

your best off doing what most people do is get the neutral balanced torque converter and the b&m flexplate with the offset notch