I had to replace mine on a 67 Barracuda too. Both my front rails weren't any good. Try getting the whole rail front to torsion bar mount (back). Check those crossmembers too.
Its so much easier if you can get rails with inner fenders attached. I had to use an air chisel to remove the rails, and it made a mess of the original inner fenders. A plasma cutter would have been great. Its a big job. Any A body 67-74 should fit , I think.
I got my rails/inner fenders from a 73 Duster.