Hi Kcwis:
Classic Ind makes a patch panel for a 73-80 C series truck. This is the only one I have seen advertised on the web on the first page of Google...there may be more that do not advertise as well.
The problem with the Classic patch panel is that it may be for a 77-80 truck which is slightly different cosmetically on the front edge...it also may be thinner gauge steel than the original hood. If these things are important to you, call and ask the guys at Classic for photos and measurements on their patch panel.
Good luck,
Henry