im not sure about this, so dont quote me on it....but i do beleave that 4.0 in some explorers have a huge radiator. Like as in thickness. (i think its a 3 row?)
I have seen them before, but the reason i say dont quote me on it is becuase ive only really seen them in earlyier explorers like 1992 range. Idk if they still put the same radiator in the newer ones, or if the rad from the 92 will even work for your 2000.
What i dont get is my 03 ranger has a 4.0 sohc and it has a two row rad? maybe the radiator itself is bigger, idk....
as for the 5.0 rad, dont worry about doing that....if the rad is good enough for a v8 then its just overkill for your engine. It wont be any better unless your driving your truck in like 130 degree weather or something. If you over heat with a rad ment for the 4.0, then you have a cooling problem... infact the only time ive every overheated an engine with a properly working cooling system is by doing a long ass burnout, or by being stuck in snow and gunning the engine and hardly moving for about 15 mins. so unless you plan on those kind of conditions, you dont need that big of a rad.