I think you're right as the Japs certainly looked like outtakes of the Harvards that were modified for the film "Tora,Tora,Tora".
I used to fly from Nuthampstead (site of the Barkway VOR) which was one of the early P-38 sites. Apparently the Allison engines couldn't cope with the cold, damp weather, a feeling I know well and they were soon withdrawn.