I run 40's on my standard 2.0L Zetec with a Facet 40147C pump and Purolator regulator, all of which are on 8mm ID hose, right from the tank to the front carb. I bought the Purolator PRO54 which has 8mm inlet/outlet which fits fine.
The regulator controls the pressure rather than flow so that the carbs needle valves are not overcome with petrol so a large hose would work ok, but not one that is too small.
Having said all that, when I fitted the pump/regulator I bought 3 metres of good quality 8mm fuel hose, a box of clips (not worm drive) and replaced the lot
Guy SB Lowe o *arrowup*o
The ZETEC is now running here