What if V-3420 available earlier?

[wuzak]

What's the airplane in the question?

Sorry, was talking about the B-17.

 

[tomo pauk]

Okay, it indeed seems that a really large prop (needed to transfer those 3000 HP into thrust) would've been too much, re. fuselage and/or runaway clearance. So maybe attaching it halfway between outboard and inboard (historical) nacelles, slightly above the wing?
Here is the drawing of the XB-38, BTW:

http://www.arcair.com/Rev1/101-200/Rev173-XB-35-Hiott/04.jpg

 

[wuzak]

I'm thinking contraprops, to minimise the modifications to the wing.