Here is an Ebay auction for a pair of used Hipo exhaust manifolds by Ebay member "gandharvas" with a starting bid of $1.00:
HIPO 289 K CODE 1963 COBRA FAIRLANE EXHAUST MANIFOLDS ORIGINAL C4ZE/C30E.
If you are reading this, you know what you are looking at. These are almost the holy grail of Ford parts. Factory rated at 271 horsepower, these are the real deal: genuine, original HiPo K-Code manifolds. The LH Manifold is Cast C3OE-9431-B and the RH Manifold is Cast C4ZE-9430-A.They have been used, but great, original condition. No heavy rust or metal pitting. All of the ports and surfaces look good, but the ports looks like maybe there was some delamination/flaking of the top layer due to condensation. This is natural with cast iron manifolds and shows they are used. Should clean up nicely with a flap wheel. Looks like they have been painted. I picked them up for a project that didn’t happen. Comes with new mounting bolts, donut gaskets, and stud bolts for one side. Original stud bolts still on the other side.
Clean them up and keep them original, or port match, extrude hone and ceramic coat these and you'll be happier with them than any header. Better heat retention, no torquing bolts, decent flow properties and lower under-hood temperatures.
I also have a custom, 2.25" h-pipe made for these manifolds. Let me know if you are interested in them and I will post them separately.
Let me know if you have specific questions or need specific pictures, etc.
On Jan-18-20 at 13:45:59 PST, seller added the following information:
Re: casting numbers. You can see the outline of the cast-in tag in pictures 9-11, but they aren’t very clear. They read: “5 18 5” on the drivers side and “6 2? 5” on the passengers side. Thanks! Message me for detail pictures.