I want to rehabilitate my old Dodge Class C

More power to you. There are a number of old rig refurbishment threads on this forum and those who have done it will provide advice. It is sad, however, when a project like this bogs down for health or other reasons and never gets finished. It is likely that the old appliances, plumbing, 12 and 120 volt systems electrical systems will require replacements and upgrades not to mention engine, cooling system,transmission, brakes, dash AC, wheels and tires, suspension,(etc.) that will need repairs or upgrades to make this sows ear into a silk purse that you can trust for serious motorhoming. Think it over, it's a lot like renovating a termite ridden dry rotted old house.