zombie84 said:
...It may even be slightly random, because Lucas had a very early VCR of some sort and whenever there was an old war movie on television he would tape them and take notes, and then later cut the taped footage for the rough cut.
If Lucas had gotten the greenlight for production from Fox, couldn't he have afforded actual reels to cut up for his workprint. Surely, that would be a standard production cost.
And doesn't the Making of Star Wars documentary show some of this workprint footage? I am pretty sure I remember all of the footage there of WWII movies was all black and white, which might exclude 633 Squadron.