JMO, unless you are twisting that thing some serious RPM (6500-7000+), internal balancing a 360 is money better spent elsewhere (heads). Plenty of 360's rolling around with plenty of miles on them in external balance configuration. Internal doesn't even cross my mind with a factory iron crank. If stepping up to a forged 3.58 crank, then yes. internal balance. Stocker stuff, nope.
Sucks this happened to you. Hope you get it fixed and running soon.