1998, it is probably time to replace the wires anyway.
Motorcraft wires might available at Walmart, certainly any large, discount auto parts stores.
Tip - place a dab of silicone dielectric grease on the contact on each end of the wire and a bit on the inside of boot on each end. They will slide on easily (burp any trapped air) and you will have no corrosion. Spend a couple extra bucks and replace the cap and rotor. Apply dielectric grease to the contacts on the inside of the cap and the end of the rotor.
Trust me. This is one of those "Once of Prevention ..." things !
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Peace, it's our only chance
1998 E150 Club Wagon, 4.6L Modular, E4OD
2007 Milan. 3.0L Duratec, Aisin 6 speed AW-F21
others I look out for
2007 Escape 2wd (the mini Pumpkin), 3.0L Duratec, CD4E
2008 Mazda3 5 door, 2.3L, 5 speed manual
My advice is worth every cent you pay for it ! | 
spark plug wires 
Hybrid Mode
