Mercon III is for older trucks up to ~2000, for an 05 truck I'd go Mercon V. Check with the dealer or knowledgeable tranny shop.
dexron/mercon
You use mercon 5
Dexron ATF
Mercon transmission fluid
Mercon 5 transmission fluid
Mercon ----------------------- C 6
Yes, they are interchangeable.
Motorcraft MERCON automatic transmission fluid
There are a few transmission fluids that can be used in a 1995 Ford F150. The most common fluid used would be Mercon ATF,
Mercon V ATF as per the owners manual and Ford
You can use Castrol ATF it meets DEXTRON III AND MERCON requirements. This fluid will say for use in older Fords and GM vehiclews.
Motorcraft MERCON automatic transmission fluid in your 4x4 transfer case