Walt Musciano published a construction article for the P-38 in the December 56 issue of American Modeler.  This had a span of about 40 inches or so  The plans showed the installation of either the OK Cub .14 or the K7B 23.  It was typical Musciano construction with sheeted wings and planked nacelles.  That is not a large model and a pair of Norvel .061's or the AP Wasp would get this in the air as long as the overall weight is kept within reason.  Rough calculation show this to be only about 180 sq in.  We have found with the multi-engine 1/2A profile scale events that these twins work just fine with around 200 sq in.  (Actually, the range could be probably from less than 150 to more than 250 sq in.  (Need to remember a good 1/2A stunt ship with 220 sq in or so at 11 or 12 oz is full stant pattern capable.)  Plans are available from the AMA plans service.

That Musciano design was incorporated into a Berkely kiit .09 to .19 engines.  I think it was the same design except the construction was based on carved blocks for the nacells  (I have the kit and plans.)  Kit plans are available from the AMA plans service.  A pair of Norvel .061 or some of the .09 engines on the market would do just fine for this.

Keith