Fuel pumps push better then they pull. So you get better fuel flow with the filter between the pump and the carb (the original design).
However, if you have a fuel tank with sediment, you really need one before the fuel pump. I used filters in both places when I was running with a cruddy tank. When I finally got a good tank installed, I put in a stock glass filter (with replaceable element) just in front of the carb.
