cooler with a bigger sump?

I would have to remove the viscous fan then though wouldn't I?

Are they really that much better?

No, and no. I was thinking of installing it on front of the radiator, assuming there's a way to do that in a Rangie. At slow speeds and slow revs the standard fans don't keep up with the required airflow. A lecky fan allows you to insist that air flows regardless of revs and speed.

My Stage 1 has just electric, and under high load it warms up, too, but at least it doesn't overheat.

Just a followup on djam1's comment on radiators, different vehicle but same concept.
I had a radiator custom built for a 1.6 Isuzu I'd shoehorned into a Sierra (leave it at that, it was a bad idea), of course the space was restrictive so the radiator was not as physically big as would ideally have been.

Anyways I was told the PFI (fins per inch) has a greater efficiency than adding an extra row to the core (say 2-core to 3-core is common). Mine ended up 14FPI whereas I think it was 11 or 12FPI for a standard Sierra, (was a long time ago). That temp never budged, no matter how hard I worked it.
Only concern I had was mud etc clogging it up so I had a screen of flymesh behind the grill but also I was wary of it and so I just made a conscious effort to ensure it was kept clean.

Worth consideration if anyone is planning to upgrade their radiator.