Your current converter is neutral balance if it came from a 273 or 318. You are kinda confusing me with the "early" magnum. Is it a magnum or an LA 360? Just know that the two are balanced different and the magnum needs the tone ring flexplate.
Travis..

70 GTX project, orig 440-4, 4 spd, track pack, FC7, stripper/street racer special.