There are a decent number of gen II people running the Walbro 255, some with problems and some without. The gen II has a different return system than the gen I and when using the Walbro it will suck air instead of gas if you let the tank get below about 2-3 gallons. The basket has to be modified, but I bought mine with a modified basket. Tradeoffs? Higher HP potential with the Walbro but possible shorter pump life due to the PWM system.
I am still debating whether or not to use it as I have heard both sides and still do not know whether I am going supercharged or not.
I know people were using the Aviator pump and they liked the SVT Focus pump because it comes with the basket and is a direct fit.