If you're building the bottom end why not just have it balanced. (you should anyway) and then everything will be neutral. (balancer, flex plate and converter.)
The only way to get an internal balance with a stock 360 crank, and the pistons and rods he is using, is to add Mallory metal. So now you are talking $350-450-500 to get a shop to do all of that.
Never had any bottom end balanced for my rally cars or mid-performance tuff. The rally cars ran 6000 RPM regularly for the 2.6L turbo and 8k RPM over and over for the 1.9L N-A. Never broke a thing and bearing wear etc. was always good. Just stock piston & rod weights and stock crank balance.
