Pulled stright from the '96 Aerostar/Ranger/Explorer manual...
I did a quick search of Motorcrafts website to find out what grade oil meets the specifications shown in that pic, and Ford Spec WSP-M2C197-A = 80W90. Click Here, go to 2nd page and look at the key/legend..... http://www.fcsdchemicalsandlubricant...f/axlelube.pdf
You know the price of that modifier at Ford, how about asking them what your truck calls for? Or...I know it's a 13yr old truck, but do you have an owners manual?
You'll be fine with a 75W-90 or 80W-90. Does it get really cold in Kansas? I would highly advice against a 140 oil for cold environments. It's really thick and turns to goo in cold weather.
Friction Modifier....not needed, but my axle guy suggests it even for open differentials, makes the oil even more slick and he won't build an axle together without it. So I run it in my locked axle.
mkay...I think I covered all your bases. Gave you info straight from Ford, and gave you what you didn't want...my opinion. lol.