RE: engine's for P38
This is not a good airplane for a multi engine beginner and it is a very poor choice as a first twin.
The Wing is however a superb P-38 and a far superior flyer to the Royal of about the same size and wing area. Done properly with approriate engines it will come out 4 pounds or more lighter than the Royal. Both of mine came in at just over 9 pounds with Springair retracts. The Royal I built many years ago with fixed gear and two two stroke sixtys came in at 14 pounds all with the same wing are, think about that.
The wing is light and was intended for two strokes Period. There is no room within the cowls for long fourstrokes, also room for fuel tankage is very limited for big engines.
Both of My Wings are powered currently by TT 46 and Ultra thrust pipes. Anything more that 46/55 two stroke is going to result in an overweight airplane with diminished performance.
If you do this mount the engines with out thrust and on both sides about four degrees. Do not omit. Counter rotation is over rated and a crutch everyone wants rather than getting a mentor who knows the procedure to successfully fly and surviving on one engine. This is the key to your airplanes survival is that technique. It is not intuitive and It makes no differerance how much single engine experiance one may have.
I have raced both my wings in warbird pylon and love them, anything over 46/55 or foustrokes would just ruin the airplanes marvelous handeling.
John