I believe the whole reason behing platinum plugs is that they give you an extended service interval, not actually any better performance.
Auto manufacturers exploited the platinum plugs to their benefit. They could advertise to the consumer an unheard of 100k mile tune-up! What a selling advantage for them. What the consumer didn't realize is that when buying that transverse engine minivan with the engine half way under the dash, is that the tune up had to be done from underneath AND you had to be double joited in your elbow & wrist. Platinum plugs was the answer to this problem-who was going to buy a car that had to have a $250 tune-up every 30k miles? Nobody.
There is no reason to run platinums in the 4.0 simply because of the spark plug access. Even if you did run platinums, it would be wise to R&R them every 30k to clean/gap/apply anti-seize to prevent seizing.
Just run the standard resistor champions-
Replace them every 30k miles, gap them properly, use anti-seize even if the cylinder head is not aluminum, use a spark plug socket WITH the rubber insert, torque them properly, and as straight on as possible to prevent an unknown cracked ceramic insulator that could cause drivability problems. Always have it quiet when torquing your plugs so you can listen for a "tink" that might be you cracking your ceramic. Use dielectric grease sparingly in the wire boot, don't use oily hands when handling the new plugs, and for petes sake, change out your valve cover gasket if it's leaking oil into your spark plug recess and onto your wires!
Chrysler did extensive dyno/performance/emission testing with these plugs for that engine and there is no good reason to circumvent their efforts.
I also recommend autolite/motorcraft for ford, and ac-delco for GM, NGK/ND for imports, and Bosch for european-(in general, but always the OEM plug).
And I'm just not a believer in spark plug cross referencing.