I’d really love to see what amount of detail you could get from the speeder shot. You could always add grain to it afterwards to make it appear more natural. Since cleaning up the shot at all is already revisionism in itself, I’d say it’s fair to cheat a bit like that.
I would say cleaning up the shot to approach the image on the original negative is not revisionism. Cleaning up the shot to recover the maximum amount of detail using modern techniques with the purpose to recover an enhanced image beyond what was possible in 1977 is revisionism in my view.