Lots of misconceptions here I see...
J.B. hit the nail on the head regarding fan shrouds.
Loose the shroud, you're creating eddies within the core that make hot spots and significantly weaken the tubes.
Also... if you've got to run your fan when you're doing highway speeds... you've got something significantly wrong with airflow and cooling... The fan(s) on ALL factory vehicles (I'm not talking about a supermodified sand-rail here...) are used when the vehicle is immobile. When the vehicle is in motion, the air passing over the fins is what cools it. If the vehicle stops, the fan is used to keep the air moving over the fins and help the radiator do it's job.
Regarding 'rows' 'cores' and 'passes'... you've got mixed info here.
The core of a radiator has tubes in it. Connected to the tubes are fins which wick the heat away from the tubes.
This is an image of the TANK END of a 3-row radiator core, with the header plate still attached.
Notice there are 3, parallel tubes per course. Assuming that each of the tubes is approximately 1" in width, the thickness of this core would be ABOUT 3".
Here is a 2-row core. Assuming that each of these tubes is 1.5" in width, you still have a 3" core. Fewer rows, but the same thickness profile. Alternatively, each of these tubes could be 1" and you'd have a 2" core... Keep in mind, I have sold radiators that have been up to 6-row... (about 4 inches thick)
Now... all this row/core stuff is TOTALLY different than "passes". A radiator for a Jeep is typically single pass... this means there are no baffles in the tanks directing the flow of coolant. Hot coolant comes in at one tank and cooler coolant goes out at the other tank.
In a 2-pass radiator, you would have your inlet and outlet on the same tank. In a 3-pass radiator, your inlet and outlet are on opposite tanks again. The "pass" refers to how many times the coolant passes across the core. a 2-pass, the coolant flows like a big letter C. in a 3-pass it makes a zig-zag.
This is the best example I can give regarding how a 'pass' works in a rad core:
Imagine the 180* turns at the end as a radiator tank with a baffle in it. The coolant doesn't go in on one side and come out on the other, it goes in and zig-zags back and forth across the core. In a multi-core radiator, a 3-pass setup is desirable as it gives the coolant MORE of a chance to decrease in temp.
This also brings up ANOTHER issue... how much cooling is TOO MUCH cooling? Are you running a big bored out engine, chugging up steep hills with massive tires and street-gears?... you probably want a bigger radiator with multiple cores and passes and a pusher/puller fan setup... Do you drive your rig on the highway and play weekend warrior too? The stock rad will almost definitely be 100% all you need.
Go cooling the engine too much, you'll wear out your t-stat prematurely and do some funky things to the engine... think what would happen if every time the stat opened, that 210* engine got flushed with 110* coolant... then the stat closes and bam, it's back up to 210*, then flooded again with 110* coolant... Lotta stress on the innards and seals. If your rad is too big, it cools too much. There's a reason why the big f-350's run a radiator that's the size of a jeep hood and why the honda accord runs a radiator that's the size of an MG midget's door.
I've also read some comments about folks getting their new rads without epoxy on them. I'm not aware of ANY all-aluminum radiator that uses ANY epoxy anywhere on them. At least not any that are worth the average rate of an aluminum rad! Most plastic-aluminum radiators (typical nowadays and the stock selection for the newer Wranglers) do have epoxy on them holding the header plate to the core. Remember, the core is just the fins and tubes. The header plate is what the tank attaches to and what the tubes go through, into the tank. Typically those tube-ends are epoxy'd into the header plate.
On the flip-side, copper/brass radiators use a brass tank and copper core. The tubes are soldered into the header plate and the tanks are soldered to the head plates. The filler neck is also usually soldered into the tank along with any nipples for overflow, ect.
Copper/brass radiators are fairly inexpensive to repair as long as you know of a good and REPUTABLE shop. For folks in the greater Denver metro area, I highly recommend Ed from Gold Star Radiator on south broadway for repairs. He's right across the street from Performance Radiator. (Used to work there)
If anyone in that area is interested in the details of how all this stuff works and actually see some hands-on examples (they have cross-cut core samples of ALL kinds at the front counter) stop by and talk to Bruce, Joe or Ruben at Performance.... usually Saturdays are slow so they'd love a chance to chit-chat.
They can explain exactly why hotspots are bad and show examples of tubes that have burned through, tanks that have blown apart from steam pockets, even what happens inside a cooling system when you use tap water instead of distilled water. They've got little tanks displaying the differences in coolant and what it does to the metal, plus tanks that have buckets of white dust in them from the minerals in tap water.
Anyway... while the all-aluminum rads look really pretty, I wouldn't suggest them as a way to go when it comes to a Jeep. If you want a rugged upgrade for your rig, go with copper/brass. If you blow a tube on a trail, a pinch with some pliers and small pocket-torch and a piece of solder will seal it up enough to get you home and probably into the next week!
Last I knew, most of us don't carry tig welders on a trailride and as much as I love working on my rig... pulling and replacing my radiator once or twice a summer isn't an idea of fun to me.
My upgraded rad will definitely be copper/brass when the stock one needs to be replaced.
Wow... ok, rant off!