To answer correctly it is very important to know the year and engine you have.
For 97 and 98, 2wd and 4wd 4.6 and 5.4 without a/c the cooling system needs 17.9 quarts and with a/c 19.4 quarts.
Different if it is an Expy or Navi.
I am buying today the antifreeze for a flush tomorrow. I suggest you to get a repair manual. They have all the information you need and how to do it correctly. I have the Haynes manual and it's been like a school for me.
1998 F150 4x4 Lariat Supercab Flareside 5.4L in Oxford White/gold, ORP, Tow Package, 3.55 Gears.
K&N FIPK, Stepshield door sill protectors, Performance Accesories 3" body lift, Lift Lips, Gabriel Gas Ryder LT VST Shocks and Daystar front anti-sway bar polyurethane bushings.
Photos at: http://www.communicomgroup.com/jmtruck