I just ran the mission in B-26s. I rolled with 75% gas to see how far that would get me. Once up from A53 I started climbing to the east until sector 11.17.5 Then turned south leveling off at 19K. At that alt max MP is at 39 inches and you pull 279mph will doors open. After heading south for about three sectors I turned west at 11.14.8 heading for the city. With 75% I had about 61 minutes of fuel when I drooped my bombs and a max range of some 400+ miles.
To the guys flying the bombers in the mission I would suggest 50%, you could probably make it with 25% but if you get a fuel leak you might not make it home.
I ha vent flown it in the P38 or P47 but my first guess would be 75% and a drop tank.