Although the rusted area above the windshield can be replaced with a homemade patch panel I would suggest a cab transplant if you have other areas of rust through. I have located a good 58 cab in a yard in Vernon, Tx that may work for you if the years are interchangeable. I had my eye on it for a future project but I am sure I will come across another in time. It is already stripped and sitting on some old rims. Contact me and I will give you the name of the yard if you want to go that route.
