FWIW, I bought my F250 (3/4 ton, LWB) brand new in 1989. I never saw it when it came in on the truck. It was driven straight to a aftermarket shop. They pulled the bed off, cut the frame in half and shortened it to SWB specs.
Then put a SWB body on it, painted it, and sent it to me. Then I started doing some modifying.
No rock climbing here in FL, but I'm still driving that truck today, and the twisting stress that has been done to it crossing rivers and coming down off banks is easily equivalent to some of the usual rock stuff.
Despite both sides of the frame being cut in half, its still as straight and strong as when I first got it.
You should be able to make your cracked frame as strong as factory, and maybe even stronger. Just make sure to do a very careful inspection to find all the cracks and fix them at the same time.
Maybe a pressure wash, and parking it with first one wheel and then another on a small block to stress and open any other cracks then mark them with paint or chalk.