I'd keep it and use it if it's in good shape. I'd also make sure that the heat riser butterfly was fully functional and that the blank-off plate between the intake and exhaust manifolds was intact. Otherwise, you will have problems with it eventually.
My original '78 CA exhaust manifold was cracked in so many places that it was just not repairable. Many years ago I replaced it with a Federal manifold. Installation of a Federal exhaust manifold requires use of a Federal head pipe and a Federal EGR pipe (or custom pipes for both).