the fuel filter on the 92 topaz is located on the right inside fender, on the 90 it may be in the same place, if not you can follow the fuel line from the gas tank to the front of the vehicle and it should be visible.
The fuel filter is located on the passenger side frame rail just ahead of the rear wheel. Drivers side, mounted to the frame. The fuel filter on a 1991 Caprice is located on the passenger side frame rail just ahead of the rear wheel.
the fuel filter is usually located near the fuel tank on the driver side of the vehicle. If you look under the truck and see the tank. follow the line back towards the engine and you should see the fuel filter.