Your local parts store should be able to help you out. Regarding parts and prices.
According to the 1998 Ford Expedition Owner Guide : The fog lamps use ( bulb # 899 )
It takes a 9007.
I believe the are 16"..
Door Speakers are 6x8...
All 4 doors speakers on the Ford Expedition are 6x8.
My 4x4 Expedition has 265/70/17......if you have 16" wheels it should be 255/70/16
In a 1998 Ford Expedition XLT : You either have the 4.6 litre / 281 cubic inch V8 or the 5.4 litre / 330 cubic inch V8 engine
6X8 inch speakers for front and rear doors.
The 1998 Ford Expedition had a mid-year production change which affected the wiper system. See sources and related links below for the best explanation of how to determine correct wipers.
The Ford Expedition's where first built in 1997- Present. It depend on the year and model too. My Old 1998 Ford Expedition XLT had a 30 Gallon Gas Tank.
Depending on rim size; Original Equipment Size 1:255/70-16 Original Equipment Size 2:265/70-17
9006 HB4