Cooling is a complicated issue and many things effect it.
Last summer on our annual Eastern Sierra trip, the new 4.6 stroker ran cool with the Mopar HD radiator. This summer, it got hot going up Sherwood grade, north of Bishop.
Pulling over to let it cool at an high idle, it dawned on me that I didn't hear the mechanical fan roaring.
I ordered a new fan clutch at Napa, in Mammoth, and after installing it, the engine is now running in its normal temperature range. That was three weeks ago and we are now up in British Columbia and it's still running fine.
Clutch fans do not seem to have a long life in XJ, a new one was used when the stroker was installed less than two years ago.
In the past I tried running a ZJ fan clutch . It worked great, actually too well in the winter, at keeping the temps down but the constant noise and drop in mileage convinced me to remove it.
A stock fan clutch works OK if still in good condition.
Having a two piece fan shroud simplifies changing the clutch, turning it into a 20 minute job, done at our campsite.
I'm a happy camper.