Should I leave the heater box out?

Ditto to Cuda6. Mine was A/C box that weighed 48 lb. Note: a non A/C heater box will NOT fit in a car with factory A/C. The firewalls are different. It is possible to make a box around the heater core and fab up brackets for install. Someone mentioned Vintage Air heater box, sound advise. I would suggest a heater/ defroster from a forklift or a farm tractor. They are small/compact/light and work like mad. Hopes this helps