I've never seen a frame rust thru right there yet, and dont know of any kits. Mine looked kinda bad at the pocket until I sandblasted, but it cleaned up fine. The metal was strong to a stout pik hammer.

If it is that bad, you can still find subframes... maybe not a '67 though... the later ones bolt in but are different in the bumpstops and maybe a couple drilled holes..

You can get some good pics of a similar frame that has the cntrl-arm and shock mount cut off for some mods here:
http://www.x1nova.com/fabrication.html