On my lemons car, I never had any engine overheating issues. We actually had the thicker rad as a spare with us at every race, but never installed it. We ran the stock rad from a 94-97 V6 bird, the stock 94-97 bird electric fan wired to high speed whenever the key was on, and a 180 degree thermostat. The car would get up to 220-230, but never went any higher. But then again, when you are moving at 120mph, there is a lot of air being forced across the rad. You are in an odd situation because you have just as much load on the engine as we did, but don’t have the airspeed to help with cooling.
As for what I think you should try, a good oil cooler like that will help. You might actually want to delete the Explorer oil cooler. The oil to water cooler is going to be putting all that heat into the coolant, and if you can delete that and instead have it’s own oil to air cooler, that will help. Some Explorer motors actually have an oil filter adapter that puts the filter in the same location, but doesn’t have the cooler. Don’t mount the oil cooler in front of the rad, mount it off to the side somewhere so it isn’t preheating the air going across the rad. If you haven’t already, make sure the fan is on high whenever the key is on or engine is running. We did that by taking the wire that triggers the fuel pump relay, and having it also trigger another relay for the fan. If you don’t have any thermostat in there, definitely install one, or at least a restrictor. Taking an old thermostat and just breaking the center out of it works fine and costs nothing but the gasket. My final thought, I don’t know if you have to run straight water or if you are allowed to run any coolant you want, but if you are allowed to run it, Evan’s waterless coolant is expensive, but good for about a 10 degree drop in coolant temps. I have a couple customers with C2 vettes (one small block, one big block), and both of them would always overheat on the highway. On the big block car we tried air dams, fan clutch, flex fan, electric fan, shrouds, foam between the shroud and the rad, nothing made any difference. We put the evans coolant in as a last ditch effort, and it has been fine for years now! When the small block car first came in for the same issue, I immediately went right to the evans coolant, and that car has also been fine now for several years.