What a co-inkydink! I was just flipping through my references on the same subject. "Warpath Across the Pacific" by Lawrence J. Hickey has
numerous photos and profiles, including natural metal finished types.
My favorite is a B-25J-22 #44-29577, Lady Lil of the 498th BS, Clark Field, May 1945.
Squadron Signal In Action #34 has a few photos and a great color profile of a 12th BG B-25-J, Sunday Punch.
Several more MTO natural metal Mitchells are profiled in the Osprey
Combat Aircraft #32. Some neat stuff in this one and it is readily available and not too expensive.
Detail & Scale #60 is loaded with color interior shots and detail photos of just about everything you would want to stick into or on your "J".
Don't mean nothin'