I have fitted filters to a pair of Humbers last year with twin tanks. I got a fitting with a fuel conector fitting the same as that fitted to the engine and screwed it into the filter(blocking 1 in and 1 out). This allows for you to change the tanks over on the filter housing instead of the engine. Plus you can still use all of your existing fuel lines, all you need is a bit of hose to go from the filter housing to the engine.
HTH