Overheating and the oil pressure drop?

I think the vehicle listed above is the ‘Sport’ version according to the VIN. My mechanic has installed a Jasper remanufactured 4.0 liter inline 6. Which is an exact replacement. It has been exchanged for a warranty with Jasper because of overheating and the oil pressure drop. The new engine is now installed. He has also installed several new thermostats to troubleshoot. It has a new radiator, water pump, fan clutch, etc. Everything functions fine. It reads a little warmer on the cluster temperature gauge than it used to with the old engine. Where it used to be 210 is now 215f. After its warmed up and on a hot Arizona day the Jeep will overheat when I shut it off at a gas station. Sometimes deep into the red line and I have to wait for it to cool off, sometimes not so hot and I can start it and it drops temperature immediately as the fan gets going and it starts moving. I instructed him to use MOPAR coolant at 60/40 mix. I noticed this new engine is very sluggish because of overdrive. I turned that off on the highway so I can travel at highway speeds without having to floor it constantly. The transmission was rebuilt some years ago, it is a 4-speed automatic. I feel that we are at a point where I need to buy an aluminum performance radiator and a hood louver to help this engine drive cooler, but I don't want to do that and have it remain the same. I also want to mention that we have a new remanufactured PCM and the Jeep has some other upgrades. Flowmaster exhaust all the way back with cats, Cold Air intake with KN filter, 33” tires on a 4” suspension lift, I have had it regeared to 4.56. There is a slip yoke eliminator and new drive shafts, front and rear. I just yesterday updated my Superchip and tuned it to 91 performance. This really helped with the highway drive. The sluggishness is gone.
What are we missing with the engine that is causing it to run hot and overheat when shut off? All of the upgrades mentioned were on it before the engine swap. It used to never overheat until the engine swap.
Thanks for reading and helping!