Those are the frame horns, you shouldn't have too hard of a time finding them, as long bed/ short bed are the same, it's just welding and measuring that will take some time. So, I'd say you can rest easy, that's not as big of a problem as it may seem.
Have a good one!
Ben Smith
__________________
"Persistence is the twin sister of Excellence.one is a matter of quality,the other, a matter of time"
“Serious Black” my 1971 Short Bed Fleetside Sold to
an outstanding man in Lees Summit,Mo. “Gone, but by no means,Forgotten”