You didn't mention what model Jeep you have, but I'm assuming it's a CJ, and if that's the case you don't have much real estate for a huge radiator. A remote oil cooler with a fan may be an option to loose some heat.
I have a 69 Bronco Crawler that is presently on hiatus due to a sick 289.
I had cooling issues and vapor lock problems with it while crawling. I put a body lift on it , hogged out a big piece of the inner fenders, installed a axillary pusher electric fan and put a Thunderbolt scoop on it.
Getting the hot air out of the engine compartment fixed all my problems. A body lift may also give you some room for a little more radiator.
I heard all the horror stories about body lifts, but I know 4 guys with body lifts on their crawling Broncos and so far none of us have a had any problems..