I agree, the stock Ranger cooling sys seems A-OK with plenty of "margin". I've been off-road in S. AZ, 118 degrees outside, 4-Low, A/C on, stereo blaring, steep grade climbing, and the temp gauge stays where it always is, mid-range. Ergo, if I replaced anything, it'd be an EXACT replacement.
NO e-fan will have the cooling capacity of the OEM mechanical!
While installing an e-fan on a Ranger seems like the proverbial "solution looking for a (non-existent) problem", and not something I'd ever do, you can't categorically state that some e-fans won't move more CFMs than the OEM belt-drive... of course if the mondo e-fan requires a larger alternator to drive it, that would be a clue-by-4 that you're going overboard, and doing a mod just because it "sounds cool"... no pun intended.