I upgraded mine to a high amp alternator from a Grand Cherokee V8, 135 amp IIRC. Bolt in and plug in to the factory harness(91-92 MJ only), larger casing but still fits without interference. Mind you I several lights, a winch and other various electrical gizmo's, and more to add so wanted the headroom for charging a second battery as well. As for a good aftermarket alternator, AC Delco and Bosch are readily available. For the older Comanche's different alternator and wiring.