P-38's didn't have good gun heaters, or pilot heaters. Also the Lockheed "Rube Goldberg" system for the semi-automatic turbo system was controlled by a combo of mechanical selection of the throttle and propeller controls, and this sent a sense through an electrical system to the wastegate, and intercoolers that was controlled by small orifice lines with engine oil. It worked well in temperatures close to Southern California. I think any 100 octane fuel worked fine, and the airplane was used for some time in England.
P-47's were long range fighters too, they used Lockheed 165 gallon drop tanks on the D models with wing pylons, (the Army wouldn't let the manufacturers use external tanks until 1943 showed that their dictates were all wet).
The reason the Mustang took precedence in my study is that is cost the least. The Lockheed was the most expensive at well over 100,000 dollars, the Thunderbolt was up in the 90's and the Mustang was about 55,000 dollars.
Chris...