Everything you need can be found on
www.fordpartsonline.com just use their catalog. You need 2 idler pulleys (though only one of them seems to get worn, other seems to stay good), tensioner, and belt, might as well do water pump, and serpentine belt and any associated pulleys that seem to be on the way out. Also add an UDP if you're into performance... It's a heck of a job though, so be ready. 2 parts you'll won't find on fpo are following, but call them and they can get you these parts:
W700001-S1309
F5RZ-6L273-A
Two small parts that hook onto the tensioner when you put it on. Get a haynes manual and you'll see.