go the the LMC truck web site and look.
The 1970-1979 Ford F-Series Pickup takes 14" or 15" replacement wiper blades on both sides front.
1979 ford 250 pickup truck
The 1997 Ford F-Series Pickup takes 22" replacement wiper blades on both sides front.
Mine's in the Right Side front Valve Cover
The 1980-1996 Ford F-Series Pickup takes 18" replacement wiper blades on both sides front.
The 2009-2010 Ford F-Series Pickup takes 22" replacement wiper blades on both sides front.
The 1999-2008 Ford F-Series Pickup takes 20" replacement wiper blades on both sides front.
I had 31 x 10.50 on my 79'
DOT 3 will work just fine
The 1998 Ford F-Series Pickup takes EITHER 20" or 22" replacement wiper blades on both sides front. Measure your original wipers to determine which.
The 2008 Ford F150 doesn't have a vent window. They do come with a Vent visor so that you can roll your window down a little bit without being in the elements, a replacement will cost you about $50.
Dealer? Salvage Yard? e-bay? Craig's list? Hemmings?