360 magnum will work just fine with external balance, order the correct flexplate and damper and be done with it; why bother with the internal balancing; you'll blow the engine before you have issues with external balancing if correct parts are used
no you can not run a 2 wire alternator same as a GM unit; they need to be externally regulated, stock the computer controls the (in magnum engine) but stock 2 wire voltage regulator will work fine