First, they really do exist. But not in a Jeep. Someone swapped it in.
The engine was used in AMC Hornets, Javelins, Concords, Pacers and Spirits. Knowing how the parts counters work with computers, try telling the guy the car is a 1982 Hornet or a Concord.
When you own a Jeep you learn that Jeep really stands for Just Employ Everybody's Parts. AMC outsourced everything. It's not uncommon to have a Ford ignition system and a GM Delco alternator, etc. Jeep owners have to lie to countermen all the time.
Paved roads are just for getting you to the starting point!