Okay, the house is 75 years old. We will eventually remove the electric box and put in new wiring. Until then, I need a wire run to the garage to power a light out there and a chest type freezer. I have an electric wall heater in the downstairs mud room bathroom, which I would like to disconnect. Can I use the wiring to that heater to run wire to the garage to power the freezer and overhead light? Thanks!

You first need to check the voltage on the heater, it is likely 240 vac. Also check the heater for a neutral.