If the diagram decal is not under the hood, your best bet would be to visit your local library and find a reference specific to your vehicle. I don't think reference books are available for checkout, but you can make copies of the diagrams there.
Chilton manual, i have looked online for a wile for a diagram... the closest year they have is 1997 online... and its a little different
www.promanuals.com/serviceparts/2004-mazda-b4000-truck-owners-manual-automated-download
The recommended spark plug gap for a 1998 Mazda B4000 is .054"
NO, the Mazda B4000 is basically a re-badged Ford Ranger. The 4.0 L engine has a timing chain and not a belt.
where i look only year 1994 mazda b4000 truck -fuel sending that find hard time
In the engine bay
Instructions on how to remove a 1994 B4000 Mazda 4 wheel drive transmission
4.0 l ford engine
Just behind the battery
on the oil pan
Replace the fuel filter.
Above the fog light on the driver side of the truck