Replacing a 273 motor for a 5.9 360 Motor Question

All 360s are externally balanced.This means the balancer and flexplate have application specific weights.You will need a 360 flywheel.You run your 273 flywheel,you will get bad vibrations and kill your new motor with time.A tie strap from Summit(or a peice of hardware store chain) would be a excellent idea.Your car will scoot with that engine.