An original heater is a great trinket to add to a vintage Jeep. This dealer accessory, manufactured by Harrison, fit above the passenger's feet. (An earlier version, a small cube, fit above the driver's feet instead.) You can easily convince your better half that the purchase was strictly for her benefit, to keep her toes warm, and it won't cost you a single WillysPoint. There is no need to tell her that these are nicknamed "Placebo Heaters" because of the dismal heat output. The coolant may never get very warm during colder ambient temperatures because the stock thermostat is designed to start opening at 150 degrees F.

Here is my starting point, not in bad shape overall. Note the flat boss towards the right side. Harrison manufactured this heater for other vehicles as well, and some deluxe versions had a lever that operated an internal baffle to redirect airflow: