Yeah, I also took some pics of the '68 F100 LWB frame, but had to do it from inside the frame rails, due to a huge bolt-on/weld-on trailer hook-up that's bolted to the outside of the frame. If I'd have looked at that a little closer I'd have seen that it was the same as the F250 pic I posted.
And I also verified that difference in bed size yesterday....it's EXACTLY 20 inches.
I might have to try to find a place for these pics somewhere on the website, as a reference.