I have a heater core from Performance Radiator in my '06 LJ. I chose it over the considerably more expensive Mopar unit based on the recommendation of my local radiator shop (one of the last old school radiator shops still in existence and favored by the hot rodders in my area.) When asked why he recommended them, his answer was that he warranties his work and isn't in the business of using shit parts so has has to do jobs twice, also that he uses a Performance Radiator heater core in his own TJ. Those were good enough reasons for me.
Its been three years and no issues so far. YMMV.
https://www.performanceradiator.com/