i have done this to r33 gt-r, i was worried abaut the little holes on bottom of walbro, i asked from walbro factory abaut the holes and they say this pump needs to be submerged all the time, if you put it on normal place on r33-r34gt-r( abaut half tank), it takes air from the holes when you driving on low gas, and if you dont run your car a little while, when you have petrol under half tank, the pump will bleed fuel off from those holes, and then car is not gonna start until you put so much gasoline that the bottom of pump goes wet, pump needs those little holes to pressurise. i put photo of the holes..
it is tight spot to get the pump on bottom of tank, but it goes there when you try at a different angles. this photo was first fitting, and pump wasnt low enough, pump needs to be so low on the cradle as it can, just when you can put two those tightening things(dont know english name) to keep pump tight on cradle, then it is bottom of tank, and you can drive tank almost dry. it is good to change bigger cables to pump too, i put what i found on closet, hifi cables, and those are little overkill, +30 amp fuse and relay offcourse.
i love this pump, very powerfull and works with e85 without issues, and so quiet that you cant hear it if engine is running, and i have very silent exhaust.