My 360 build.

You can ask the shop how much an external balancing is before you do anything. Considering you know a few things, piston weight, the major player followed by rod weight, etc... My shop wanted me to have the balancer for the front & flywheel (4spd car) for the rear sent with everything. I had it done about 8 years ago. In these parts, (Lower New York = AKA Expensive living) my total was $325. Minor counter balance weight removed.