I recently had the same issue until my radiator blew up. Root cause on my system was a rotted out water pump, broken fan clutch and coated/clogged radiator as well as a thermostat that didn't want to fully open.

When i replaced my radiator i used some closed cell foam weatherstripping (i think it was 5/8 by 1/2 thick, double layered where it was not thick enough) to close up all the air gaps between the AC condenser and radiator as well as both fan shrouds to the radiator. Now I see temps of 214 max during hill climbing with the AC on on the freeway (its been high 90s lately where i live) and during normal cruising both in town and on the freeway i am running 200-205 now.

2001 XJ with 165k original miles on motor and trans. I am running 32s and stock gear ratios on a 4.5 inch lift so i don't know if this helps you but id say giving the gab sealing a try might be worth it for you.

Oreilly's sells that weather stripping I am talking about for 10 bucks a roll. Took 2 and 1/2 rolls to do my Jeep.

 

A 35" tire require a 4.88 gear to get it back to stock gearing 31" tire 4.10 gear, you do the math and figure the load factor he's pulling doesn't take much to figure it out.