I *never* put a filter before a pump.
The factory mechanical fuel pump already has a sediment bowl and screen, so there's nothing that can get through that screen that could foul up the pump - there simply aren't any orifices in the pump to get clogged. And remember, fuel pumps are made for developing pressure, not for developing suction.
Placing the filter after the pump allows the pump to force fuel through it quite easily. If you put the filter before the pump it's possible that the filter will slow the intake flow of fuel, meaning that the diaphragm won't fully retract (suction phase) and this will pull the pump arm away from the cam for a moment (or perhaps more, if the filter is really clogged and it takes longer for the diaphragm to return). The cam will come around and whack the arm, instead of the arm continually riding on the cam... and this can damage the cam and the arm. You want that diaphragm to quickly return and for the arm to remain in constant contact with the cam.
Now, if you're using an electric pump there's even more reason not to place the filter before the pump. There's a small capacitor in the Smiths pumps that will burn out if the pump can't pull fuel easily and once that's burned out the points on the pump will begin to arc, eventually leading to burned points and having to repeatedly whack the pump to get it going again (a familiar British car complaint).
SO...... that's a long-winded description of why NOT to put a filter before any fuel pump.