With the 2.8L V6 the only Ford overdrive that will fit is the A4LD. (Automatic, Four-speed, Light-Duty... major emphasis on LIGHT!) which was found behind the 3.0 and 4.0 V6s in Rangers, Aerostars, and Explorers.
It's a computer-controlled automatic overdrive that is an even lighter duty of the light-duty C3 Ford transmission it was based upon. They have the durability of tissue paper (I completely roasted one in 2 weeks in my 1988 Mustang LX with a 2.3) are notorious for problems with fluid pressure due to a flawed valve body that will warp when hot, and generally don't last more than 100,000 miles in even ideal conditions. My mom had the same 1989 Aerostar with the 3.0L V6 for 12 years, we put 250,000+ miles on it... we also put three A4LD transmissions in it, the only other parts that were replaced in all that time were an alternator, the water pump, and two batteries.
If you really want overdrive, a C4 with a bolt-on overdrive from Gear Vendors would be the most durable, but that would probably cost more than you paid for the car!
__________________ 1976 Ford Mustang II Ghia: 302 with a 600cfm Edelbrock carb, Edelbrock Performer 289 intake, Dynomax Blackjack headers, 2.5" exhaust with Flowmaster Super 44s. RJS 11-gallon fuel cell, C4 tranny, chrome 16" pony wheels, fuzzy dice, brown vinyl half-top, and painted in the tackiest color ever (harvest gold, that's why I call it "The Goldenrod").
Also have a 2003 Dodge Ram (lightly modded daily driver/tow rig/office/dining room/home away from home/workshop... I call it "The Big Blue Dawg".) | 
