Haggar,
Your thermostat is located where the large radiator hose connects to the
engine. there is a housing there with 2 bolts in it. Under the housing is
where the thermostat is located. Remove the bolts, and you will see the
thermostat. If you go to www.autozone.com then click on Repair Info (left
side of the screen). Click on Vehicle Repair Guides. Select 1996, FORD
TRUCK, and then the AeroStar should be there. Then click on Engine & Engine
Overhaul. Click on Thermostat on the right side. I did notice that there is
no 3.8L engine listed in this section. Are you sure you have the right
engine? I noticed it had the 2.3L listed, but you wont hardly see one of
these. Then it lists the 2.8L, and then the 3.0L. The 3.0 and the 3.8 as far
as intake design and overall engine design were so close it wont matter. The
3.0L will work for what you are trying to do. Hope this helps.
Pk