I believe I may have located the point where the new forehead was plopped down on top of Oswald. I pointed a white arrow to it.
You'll see why when I enlarge it.
Notice that above that line it looks mottled; below it, the skin looks smooth. There is a definite difference in the greyscale there. Notice that there is a slight zig-zag effect at that point, where it seems slightly misaligned, with the superior piece slightly recessed in relation to the inferior piece on our right. Notice also that you see the same kind of mottled forehead in the source photo of Young Lovelady.
I think there is an excellent chance that that is where the dividing line is between Dooman being Oswald and Doorman being Lovelady. So, below that line, he's Oswald; above that line he's Lovelady, Young Lovelady.