As pointed out, 16" wheels didn't guarantee 4.10 gears. Many had 3.73 with the larger wheels, but some had 4.10's. It wasn't special order; my sport came with them off the lot. 4.10's may have been standard on the sport with the SOHC engine, but I don't know for certain.
IOW, I beleive that Jason is correct.
Oh yeah, I don't think that there was much to the towing package on late model explorers. You would think that there would be a little extra tranny cooler, larger radiator, and HD springs along with good gearing and limited slip, but that isn't the case. I think you get the trailer light hookup and maybe a hitch (or maybe not). I think it may be entirely a dealer addon now.