Do you remember if there was a series of connected pipes going into the top of the exhaust manifold at each cylinder? There should not have been, since a motor will not have an air injection pump and an air pump. It sounds like they used an air pump piped directly through a check valve to the catalytic converter, similar to the electric pumps on Chevys. That's interesting. I didn't know that option existed. I figured they had a modified pulse-air system. It might help with a station wagon V8 conversion, since Iron Duke station wagons are crazy rare. I would never retain the manifold injection tube while rebuilding the exhaust, but I would consider keeping a catalytic converter injection pump. Did your 360 have double V belts? My '77 401 has redundant V belts everywhere, which I think is neat.
My 73 Javalin AMX had all those tubes to each exhaust manifold leg , I snapped one off trying to get it loose, thinking I could then just put a pipe plug in it. I ditched the original manifods and just stuck on a set of headers to solve it. years later I learned that those manifolds are worth some $$$ as everyone pretty much trashed them.